McDonnell And Miller MM-825J General Catalog Instructions

: June 28, 2024
: McDonnell And Miller

Table of Contents

McDonnell And Miller MM-825J General Catalog
Product Information
Product Usage Instructions
FAQs
Basic System Operation
Boiler Controls
Read User Manual Online (PDF format)
Download This Manual (PDF format)

McDonnell And Miller MM-825J General Catalog

Product Information

This McDonnell & Miller General Catalog is a comprehensive guide that provides information on various categories related to boiler and liquid level controls. It includes easy-to-identify symbols, technical specifications, glossary of terms, product line details, applications, maintenance guidelines, and warranty information.

Specifications:

Product Name: McDonnell & Miller General Catalog
Model Number: MM-825K

Product Usage Instructions

1. Basic System Operation:

Refer to the catalog for an easy-to-read guide on boiler operation, including elements that make steam and hot water boiler systems work.

2. Technical Information and Specifications:

Find detailed data to help you select the right product for your needs.

3. Products:

Explore the McDonnell & Miller product line categorized into Boiler Controls, Liquid Level Controls, and Flow Switches for industrial, residential, and commercial applications.

4. Maintenance & Replacement Interval Guidelines:

Follow the recommended maintenance intervals for different product series.
Blow down and test daily or weekly as per the series. Inspect and test annually.
Recommended replacement intervals vary based on the product series.

5. Warranty & Return Policy:

Refer to the catalog for detailed information on warranty coverage and return policy.

FAQs

Q: How often should I inspect and test the products?
- A: It is recommended to inspect and test the products annually to ensure proper functionality.
Q: What are the warranty terms?
- A: Warranty terms and coverage details can be found in the Warranty & Return Policy section of the catalog.

McDonnell & MillerTM General Catalog
MM-825K

hoW to use this cAtAloG
This guide will assist you in your tour of the McDonnell &Miller General Catalog. The information contained in the catalog is organized into 5 key categories:
· System Selection Chart · Product Selection Guide · Basic System Operation · Products · Technical Information and Specifications
Easy to identify symbols and product icons will help you specify and select the product that meets your requirements.

BAsic systeM opeRAtion…
…the encyclopedia of boiler operation. An easy-to-read, informative guide to all the basic elements that make steam and hot water boiler systems work.

technicAl infoRMAtion And specificAtions…
…full of helpful data to assure your selection is the right one.

Glossary of Terms

… a detailed description of all terms that appear in this catalog.

pRoducts…
…the complete McDonnell &Miller product line, divided into 3 primary groups:
Boiler Controls

Just check the contents pages for the associated
product icons to quickly find the control you need.

Liquid Level Controls Flow Switches

ApplicAtions…
Industrial applications

Residential applications

Commercial applications

Approval Agencies
®

MAintenAnce & ReplAceMent inteRvAl Guidelines…

…the easy to read guides will help keep you on track with suggested product maintenance and replacement intervals.

Recommended Replacement intervals

product low Water cut-offs

series
150, 157, 158, 159, 150S, 157, 158S, 159S
69, 169, 269, 369, 469
67, 767 70, 70-B
61, 63, 64, 764
42

Recommended Maintenance
Blow down and test daily inspect annually.
Inspect and test annually.

Recommended Replacement
interval (Maximum)
15 years
10 years

Blow down weekly. Inspect and test annually.
Blow down weekly. Inspect and test annually.
Blow down daily. Inspect and test annually.

10 years 10 years 10 years

Warranty & Return Policy

contents
Contents

Basic system operation . . . . . . . . . . . . . . . . .6 products: Boiler Controls . . . . . . . . . . . . . . .24
Liquid Level Controls . . . . . . . . .70 Flow Switches . . . . . . . . . . . . . . . .78

technical information and specifications Glossary of Terms . . . . . . . . . . . . . .116 Approval Agencies . . . . . . . . . . . . . .119 Maintenance . . . . . . . . . . . . . . . . . . .120 Warranty & Return Policy . . . .123-124

BoileR contRols

loW WAteR cut-offs

seRies

pAGe loW WAteR cut-offs

· For Hot Water Boilers

· For Steam Boilers

electronic

750

electronic

seRies 750

751p/752p

RB-24e

751p/752p pse-800

RB-122-e

pse-800-M

float type

764

767

pAGe
28 29 30 31 36 37 38 40 42

Contents

BoileR contRols (continued)

loW WAteR cut-offs

seRies

· Combination Low Water Cut-Off/Pump Controllers for Steam Boilers
electronic
1575

pAGe

WAteR feedeRs · Electric

47 · Mechanical

seRies Wfe 101-A

· Combination Low Water Cut-Off/Pump Controllers for Steam Boilers
float type
42s
93
94
150s

· Mechanical combination Mechanical low Water cut-offs

47/47-2 51/51-2

43
48
50 · Make-Up
44

51-s/51-s-2 53/53-2 247/247-2
21 25-A

157s

193

194

221 551-s 847 851

851-s

pAGe 52 53 54 58 59 60 56
63 62 63 66 64 65 65

Contents

vAlves
· Blow Down · Test-N-Check® · Pressure Relief

BoileR contRols (continued)

seRies

pAGe

14-B

tc-4

250

260

liQuid level contRols

conductAnce ActuAted (pRoBe type)

floAt ActuAted pneuMAtic

· General Purpose

Rs sensors

Sensors and Controls

pfc

750B-c3

pA sensors

floAt ActuAted vAlves
75

27-W

Contents
liQuid floW
· General Purpose

floW sWitches

seRies

pAGe AiR floW

fs4-3

fs4-3t

104

fs5

fs8-W

fs-250

· High Sensitivity

fs1

100

fs1-W

101

fs6

102

fs6-W

102

· Industrial

fs7-4

fs7-4e

fs7-4W

seRies Af1 Afe-1 Af2 Af3

pAGe 110 111 112 113

Basic System Operation

Basic System Operation
steam Boilers
They’ve been with us for over two hundred years, and most of the time, they’re so reliable most folks don’t give them much thought. They sit in buildings all over the world, transferring heat from fuel to water, allowing us to warm our buildings or complete our processes.
Steam boilers are simple, efficient and reliable. No machine does a better job of moving BTUs from one place to another. We’ve used them for space heating since before the United States Civil War in 1861.
Even before the Civil War, we used steam boilers for industrial processes. Today we use them to run factories, press clothes, wash dishes, pasteurize milk, sterilize medical equipment, and to heat entire cities! Their capabilities seem endless.
But despite its simplicity, any steam boiler can run into trouble if its control system doesn’t act properly. If the energy you put into the boiler exceeds what the boiler can absorb, the boiler can rupture. So you must always be on guard.
A simple safety relief valve of the right capacity and relief-pressure setting protects the boiler from over pressure. But over pressure isn’t the only thing that can threaten a steam boiler. There are also the dangers of dry firing.
Should the internal water level drop too low, the boiler can burn out. So here too, you must always be on guard. You see, a steam boiler needs its water to move the heat away from its metal surfaces. Without the right internal level of water, heat quickly accumulates. Too much heat creates a very dangerous operating condition.
Boiler manufacturers have always set up minimum safe water level requirements for their equipment. Our controls help enforce those requirements in two ways:
· By maintaining a minimum safe water level in the boiler.
· By signaling the burner to stop should the water level drop below that point.
In this brief Systems Guide we will explain how we do these two very important jobs.
What’s a “normal” Water level?
The proper steam boiler water level varies from manufacturer to manufacturer, but generally, we can say that it’s “normal” to start by manually filling the boiler to the two-thirds-full point on the gauge glass. As the boiler operates, the water will quickly turn to steam and head out toward the system (Fig. B).
Steaming takes place at a constant rate of about one-half gpm per 240,000 BTU/HR (D.O.E. Heating Capacity
6

steam Boiler fig. A
Gauge Glass two-thirds full fig. B

Basic System Operation

Rating). This is a law of physics so it doesn’t vary from manufacturer to manufacturer. If you’re working with a boiler with a rating of, say, 1,000,000 BTU/HR, you can be assured the water is turning to steam and leaving that boiler at the rate of about two gpm. And it’s leaving at speeds measured in miles per hour (sometimes exceeding 60 mph!). So it’s very important for your near-boiler piping to be correct. If it’s not, the fast moving steam will pull water out of the boiler and create problems for you in the system and the boiler.
As the water (in the form of steam) heads out toward the system, the water level in the boiler will, of course, drop. How far it drops, depends a lot on the size and condition of your piping system. You see, ideally, the water should begin to return to the boiler before the boiler’s internal water line drops to a critical point. That’s the point at which the low water cut-off will cut power to the burner, or an automatic water feeder will open.
Because the water is in the system piping and radiating during operation, the “normal” water level becomes a point that’s somewhere in the lower-third of the gauge glass (Fig. C).
Remember, you’re working with a range of operation here, not a fixed point. If the water were to stay at the top of the gauge glass all the while the burner was firing, you probably wouldn’t be making steam! So don’t get too caught up with the word “normal” because the only thing that’s normal is that the water level will rise and fall.
Boiler manufacturers, as we said before, do establish a minimum safe water level for their boilers, however. That point is usually just out of sight of the bottom of the gauge glass. Should the water level drop to this point, the boiler may be in danger of overheating. We have to find a way to protect the boiler from itself (Fig. D).
All leading authorities and insurance companies recognize this need. The ASME Code for Low Pressure Heating Boilers, for instance, specifies, “Each automatically fired steam or vapor steam boiler shall be equipped with an automatic low water fuel cut-off.” The device the code refers to is what most people in the field commonly call a “low water cut-off.” Its job is to stop the burner and protect the boiler.

Gauge Glass one-third full fig. c
Minimum Safe Water Level
Gauge Glass Minimum safe Water level fig. d

What causes a low Water
condition?
Because it’s an open system, some evaporative water loss is normal for a steam system. How much depends on the size and condition of the system. If you’re losing too much water, however, it’s time to begin troubleshooting. There are many places to look.
7

Basic System Operation

Basic System Operation
Here are a few good places to start:
· The air vents are dirty, not seating properly, and passing steam to the atmosphere.
· Someone left the boiler blowdown valve partially open. · Someone, for whatever reason, has been drawing
hot water from the boiler. · The relief valve has discharged. · The condensate pump isn’t working as it should.
The float may have come loose. The condensate may be too hot to pump.
(Check those steam traps!) · Improper near-boiler piping may be throwing water
up into the system, or causing the waterline to tilt during operation. · The wet returns may be leaking. (Always suspect any buried pipe). · A check valve may be stuck closed or partially closed. · The boiler may be foaming and priming.
Check the pH of the water. It should be between 7 and 9.
Check the condition of the water. Dirty water will prime and foam.
Check the burner’s firing rate. Over-firing can cause priming.
· The pipes may not be properly pitched. · The automatic feeder may not be working properly.
Its chamber may be filled with sediment. Its feed line may be clogged. · All of the condensate may not be returning from the system (a common problem with process applications). · The boiler metal may be corroded and leaking at the water line. Flood the boiler to its header to check for leaks.
Good troubleshooters take the time to look over the entire system before deciding what’s wrong. Take the time to do it right, and you’ll be the person with the answers.
Watching the Water level
The best way to prevent overheating damage to a boiler is to stop the burner if the water level falls too low. This is the low water cut-off’s job. There are several types of low water cut-offs you can use. Let’s look at them.
float operated low Water cut-offs
Float operated low water cut-offs have been around (Fig. E) since the 1920s and have earned a reputation worldwide for reliability. Usually, you’ll mount this type of low water cut-off directly in the boiler’s gauge glass tappings. We make “quick hook-up” fittings for these units to simplify installation.
8

series 67 float type low Water cut-off fig. e

Basic System Operation
The water level in the low water cut-off’s chamber will mimic the water level in the boiler. As the water level drops in the boiler during steaming, the level in the chamber, and the cut-off’s float drops with it. Should the float drop to the boiler’s critical low water cut-off point, the float will trip an electrical switch that’s wired in series with the burner. The burner instantly stops firing. It will stay off until the water level rises to a safe operating point.
This happens when the condensate returns from the system or when an automatic water feeder or a boiler attendant adds water to the boiler. When the level reaches a safe position, the low water cut-off will make its electrical connection and the burner will restart.
When a steam system is well balanced, the low water cut-off’s job is to stand by and wait. The situation we just described suggests that there’s something out of balance in that system. We’ll look at this again in a few minutes.
probe and float type Built-in low Water cut-offs
There are some jacketed boilers that don’t easily accept quick hook-up fittings. These boilers will often have a tapping for a built-in low water cut-off. These built-in units do the same thing as the external units we just looked at, but instead of being in a chamber, the “built-ins” are right inside the boiler where they can sense the water level directly.
We make two types of built-in low water cut-offs:
Probes The boiler manufacturer will specify the point where they’d like to have this type of low water cut-off inserted. It will usually sit just below the water line, at a point above the boiler’s crown. A probe uses the boiler’s water to complete an electrical circuit past an insulator (the center portion of the probe) back to a ground (the threaded portion of the probe). As long as water covers the probe an electronic “go” signal will travel to the burner. When water drops off the probe for a continuous ten seconds, an electronic “stop” signal goes to the burner, shutting it down and protecting the boiler from a low water condition.
At McDonnell & Miller, we manufacture several different types of probe low water cut-offs to meet any of your job applications (Fig. F).
One of those applications might involve the boiler’s water level. The water capacity of today’s boilers is considerably less than that of boilers from decades ago. Along with this, the water level operating range of today’s boilers is smaller. Further, the amplitude of surging water levels is increasing. As a result, the low water cut-off must be “smart” enough to recognize these variations and react appropriately. We have done this by

series pse-800 probe type low Water cut-off fig. f
9

Basic System Operation

Basic System Operation
incorporating delay features in the probe’s operating logic. These include a delay on break feature (DOB) which keeps the burner lit for 10 seconds after water leaves the probe. This minimizes the effects of a surging water line. Another addition the delay on make feature (DOM) allows an additional feed time of 30 seconds once water comes in contact with the probe. This minimizes rapid burner and feeder cycling by slightly elevating the water level so that water lost to steaming will return (in the form of condensate) before the water level drops below the probe.
Float Type In operation, these are similar to the external, float operated low water cut-offs we looked at before. The difference is that instead of sensing a duplicated water level outside the boiler, these units sense the level directly inside the boiler.
We make them for you in five mounting-barrel sizes (Series 69) to accommodate different boiler insulation thicknesses. When you select a built-in, float type control make sure it fits as far as possible into the boiler, without the float shield coming contact with the boiler.
When a low water cut-off stops a burner, it also stops the entire heating system. Nothing will happen until the water in the boiler returns to a safe operating level.
While this is very good for the boiler, it may not be the best thing for the system. If the heat in the building is off for too long a time, water pipes may begin to freeze.
This is where automatic water feeders come in. An automatic feeder will maintain a safe minimum water level in the boiler and keep it operating, even if the system is leaking. It keeps the system operating automatically until you can make the repairs.
combination low Water cut-offs and Automatic Water feeders
Two of our most popular and versatile feeders are the Uni-Match® and the 101A (Fig. G and H). These are ideal for use in residential or small commercial applications. They are versatile in that they are compact and they are easily installed to operate with either a probe type OR a float type low water cut- off. These feeders are always ready to add water when given the signal from the low water cut-off. The benefits they offer are the convenience of not having to manually add water and most importantly they will protect the boiler from a dry fire condition by maintaining a safe minimum water level in the boiler should a system leak occur.
If you use a mechanical automatic water feeder, you can keep your burner operating even during a power failure.
10

series Wfe uni-Match® Water feeder fig. G
series 101-A Water feeder fig. h

Basic System Operation
A mechanical feeder can also protect a boiler (Fig. I) should a fuel- regulating device malfunction, causing the burner to lock in and stay there. Or suppose someone jumps-out a control, putting the burner on continuous operation. A mechanical automatic water feeder will continue to feed the boiler whenever the level drops to the “feed” point.
Under normal circumstances, the electrical low water cut-off (the second part of the feeder/cut-off combination) is always standing by, ready to shut off the burner should something go wrong with the automatic feeder.
An automatic water feeder doesn’t feed at the two-thirds full point on the gauge glass. You set this by hand when you first start the system. As we said before, the “normal” level will range up and down as the system operates. An automatic feeder will maintain a safe minimum water line only. By doing this, it will lessen the possibility of human error.
Consider this. A boiler attendant might put too much water in a steam boiler. He doesn’t have an automatic feeder and he’s tired of checking the water level every day so he fills the boiler to the two-thirds full point while it’s operating. When the condensate returns, the boiler floods. By adding water the attendant has limited the boiler’s steam-making space. Without enough room to break free of the water, the steam will now carry water up into the system piping. This leads to higher fuel bills, uneven heating, water hammer, scale formation in the boiler and burner short-cycling. Suddenly, problems plague this system, and no one is sure why.
Automatic water feeders help you avoid these problems. They watch that water level, maintaining a safe minimum. They allow the boiler water line to rise and fall naturally through its normal operating range.
how a feeder/cut-off combination Works
During Normal Operation This is how a McDonnell & Miller feeder/cut-off combination looks on a steam boiler (Fig. J). Notice how we have it installed well below the boiler’s “normal” start-up operating range (that’s about two- thirds up the gauge glass). We don’t want it to feed while the water is out in the system as steam. Remember, the automatic water feeder is there to maintain a safe minimum water line, not a “normal,” start-up water line.
As you now see it in the drawing, the feeder is closed and the burner is firing. The boiler is working, sending steam out to the building, and both the automatic water feeder and low water cut-off are standing by.
The Feeder Opens If the boiler’s water line drops to the feeder/cut-off combination’s feeder-operating point (which is very near the bottom of the gauge glass) (Fig. K), the feed valve will open mechanically and add water to the

series 47-2 combination Mechanical Water feeder/low Water cut-off
fig. i

Feeder Cut-Off Combination

City Water Supply

Steam Boiler

Burner On
normal operation fig. J

Return Main

Feeder Cut-Off Combination

City Water Supply

Burner On

Steam Boiler

Return Main

feeder open & Burner on

fig. K

Basic System Operation

Basic System Operation
boiler. How much water will enter the boiler depends on several things, but there will always be enough to keep the boiler operating at a safe minimum water level. Once it has added the right amount of water, the feeder closes.
While this is happening, the burner continues to run because the feeder keeps the boiler from dropping to its low water cut-off point.
The Low Water Cut-Off Stops the Burner But suppose something happens and the automatic water feeder can’t keep up with the rate at which the boiler is losing water. Suppose, for instance, that a pipe breaks or someone opens a boiler drain, causing the boiler to suddenly lose water. Should this happen, the water level will drop to a preset point, and the automatic feeder/cut-off combination will instantly cut power to the burner, shutting it down and protecting the boiler from a dry-firing condition. Though the burner is off, the automatic feeder will continue to add water to the boiler in an attempt to restore a safe minimum water level (Fig. L).
As you can see, a combination mechanical water feeder and electrical low water cut-off provides you with boiler protection even if the power fails or something goes wrong in the burner circuitry.
combination Water feeders and low Water cut-offs for larger Boilers
As we said earlier, all steam boilers evaporate water at the rate of one-half gpm per 1,000 square feet EDR (240,000 BTU/HR). To satisfy a larger boiler’s needs, an automatic water feeder must be able to match the boiler’s higher steaming rate. If the feeder can’t keep up, the burner will suffer from nuisance low water shutdowns. To avoid this problem, we make automatic feeder /cut-off combinations with wider flow orifices to meet the special needs of larger boilers. The operation of these larger units is the same as the ones we just looked at. The key difference is the increased flow rate (Fig. M).
Once the larger feeder/cut-off combination satisfies the boiler’s minimum water line needs, it has to be able to close against the force of the city water pressure moving through that extra wide orifice. This calls for considerable float and lever power, and it explains why our feeder/cutoff combinations for larger boilers are bigger than those for smaller boilers. We’ve carefully engineered them to get the maximum closing force in the space we have to work with. This ensures the unit will close tightly once it’s done its job (Fig. N).
Codes call for larger boilers to have their gauge glasses mounted on water columns, rather than directly into the boiler. Consequently, we make our larger automatic
12

Feeder Cut-Off Combination

City Water Supply

Burner Off

Steam Boiler

Return Main

feeder open & Burner off

fig. l

Feeder Cut-Off Combination

City Water Supply

Burner On

Steam Boiler

Return Main

large Boilers fig. M

series 51-2 Mechanical Water feeder fig. n

Basic System Operation
water feeders and feeder/cut-off combinations without “quick hook-up” fittings. Instead, we give these larger combinations one-inch (25mm), float chamber tappings so you can mount them directly on an equalizing line.
Watching the Water level in process/ space-heating Boilers
Now let’s suppose you’re installing a steam boiler in a factory. Some of the total steam load will travel to unit heaters where it will keep the workers warm. The rest of the steam will go to a steam table in the cafeteria, a dishwasher, an oil preheater on the boiler, a few sterilizing cabinets on the plant floor, and a half dozen other process applications.
This job offers a special challenge because a good portion of the condensate won’t be working its way back to the boiler. Some of this condensate is tainted in the process and we need to handle it specially. Because of this, you’re going to have to consistently add feed water to keep this process/space heating boiler operating.
If you use a combination feeder/cut-off on this job you may run into a problem because the vertical space on the control between its “feed” point and its “cut-off” point is relatively small. The feeder might not be able to keep up with the system’s process needs, and if it can’t, the boiler might drop into a low water condition and shutdown.
It’s best to install a separate automatic feeder and low water cut-off on a job such as this when you know some condensate won’t be returning (Fig. O). Set up this way, the feeder can open fully and deliver its maximum capacity to the boiler before the low water cut-off (installed at a lower level) goes into action. By piping the system like this, you eliminate nuisance burner cut-offs while meeting both your heating and process needs.
When you select the water feeder and low water cut-off for your process/space heating application, always check to make sure the operating pressure of your system doesn’t exceed the maximum operating pressure of either control.
the importance of system Balance
steam systems With condensate pumps
Most two-pipe steam systems, and some one-pipe steam systems, need help returning condensate to the boiler (Fig. P). The pump’s job is to provide the “push” the water needs to get back into the boiler. The water leaves the boiler as steam, condenses into a liquid in the radiators and piping, and flows by gravity into a

Low Water Fuel Cut-Off

Boiler Water Feeder

City Water Supply

Burner On

Steam Boiler

Return Main

separate Water feeder Process/Semi-Process System
fig. o

Feeder Cut-Off Combination

City Water Supply

Burner On

Steam Boiler

Float

Condensate Receiver

Switch

Tank

Condensate Pump
single Boiler Balanced System
fig. p

Basic System Operation

condensate receiver. When the water level inside the receiver reaches a certain point, an electrical float switch turns the pump on. The pump quickly moves the water out of the receiver and back into the boiler.
Steam boilers served by condensate pumps also need low water protection, and our low water cut-offs serve that purpose well. You can also use an automatic water feeder or a combination feeder/cut-off on these systems. But before you do, make sure the system is well balanced. What we mean by “well balanced” is that the condensate pump should be able to return the water to the boiler before the boiler’s water level drops to a point where the low water cut-off or automatic feeder goes into action.
If the automatic water feeder adds water to the boiler (to maintain a safe minimum operating level), and then the condensate pump returns its water to the boiler, the boiler will most likely wind up with too much water. This excess water limits the boiler’s steam making space. Without enough room to break free of the water, the steam can carry water up into the system piping. That leads to higher fuel bills, uneven heating, water hammer, scale formation in the boiler and burner short cycling.
So before you use an automatic water feeder on a steam boiler that’s served by a condensate pump, check to see if the system is well balanced. It should run through its cycles without going off on low water. In other words, the condensate pump should balance the flow of water back into the boiler before the level drops to the critical, low water point. Keep in mind that a system with a condensate pump can become unbalanced if the returns clog with sediment or if any steam traps fail in an open position.
Good troubleshooters always keep their eyes wide open.
steam systems with Boiler-feed pumps
If you have a system where some steam is going for process (meaning, it won’t be coming back), or if your system isn’t well balanced, you should consider using a boiler feed pump instead of a condensate pump.
A boiler feed pump serves the same purpose as a condensate pump (Fig. Q). It provides the “push” the water needs to get back into the boiler. The difference between a condensate pump and a boiler feed pump, however, lies in the way we control the two units. Instead of having an electrical float switch inside the condensate receiver, a boiler feed pump takes its orders from a McDonnell & Miller pump controller mounted directly on the boiler.
The pump controller has two switches. The first switch (set at the higher of the two levels) operates the boiler feed pump. When the boiler needs water, the pump 14

controller recognizes the need and starts the pump. When the boiler water returns to the proper level in the gauge glass, the pump controller stops the pump. Should the pump not be able to keep up with the boiler’s need for water, the pump controller will sense this as well. The second switch (set at the lower of the two levels) will cut the electricity to the burner and protect the boiler from a low water condition (Fig. R). Feed water enters the system through a make-up water feeder in the boiler feed pump’s receiver. If you wish, you can add a feeder/cut-off combination to operate at a level a bit lower than the pump controller. This will give you a mechanically operated feeder, which will act as a backup should something go wrong with the pump controller. It will also give you a secondary low water cut-off. It’s like having a belt and suspenders for your boiler!
Pump Control and Low Water Cut-Off

Burner On

Steam Boiler

Boiler Feed Tank

City Water Supply

Boiler Feed Pump
single Boiler Unbalanced System

Make-Up Water Feeder

fig. Q

Pump Controller

Feeder Cut-Off Combination
City Water Supply

Burner On

Steam Boiler

Boiler Feed Tank

Boiler Feed Pump Make-Up Water Feeder
single Boiler Feeder/Cut-Off Combination Unbalanced System

fig. R

Basic System Operation

Meeting the needs of systems with Multiple steam Boilers
(Fig. S, T U)
The boiler on the right may be a stand-by to the boiler on the left. Every week or so, a boiler attendant might switch them, making this one the operating boiler and the other the stand by.
It’s a good idea, one we’ve used for years in larger boiler rooms. By having more than one boiler, each is able to supply the entire needs of the system. Your chances of getting caught without steam are much less.
Some systems have multiple steam boilers. The idea here is to let several boilers join forces to meet the total needs of the system. The goal is energy conservation. You steam all the boilers on start-up, and then shut a few down after you’ve heated the system and satisfied the piping pick-up load. In other words, you put the system on “simmer” after you’ve heated it completely.
Steam systems with more than one boiler often have problems if the installer fails to realize that steam is dynamic and not static. By this, we mean that steam is always moving very quickly from the boiler to the system, and as it moves, it loses pressure. And since one ounce of pressure represents a water column 13/4 in. (45mm) high, the slightest difference in pressure between any two boilers interconnected on their return sides can make a big difference in the individual water levels.
A slight burr in a pipe or fitting can create a drop in pressure. You can never tune two burners to produce the same flame. One boiler will always be closer to the system take-off than another. These things speak loudly for proper piping and thoughtful management of the boiler water line so that’s what we’ll look at next.

Multiple Boiler systems with a Boiler feed pump and Motorized Return valves
Here we have two boilers served by a single boiler feed pump (Fig. S). One boiler may be a stand by to the other, or they may be sharing the total load. For piping purposes, we’d handle either application the same way.
Notice how the condensate returns are independent. Each flows from the boiler feed pump receiver to the boiler through a motorized valve. This is an important detail. If you were to interconnect the returns, the water from one boiler would flow into the other.
Steam Moves Remember, steam is dynamic, not static. Water doesn’t “seek its own” level when the steam is moving out of the boiler. The slightest difference in firing rate or piping pressure drop between the two boilers will cause one to flood and the other to shut down due to a low water condition. This is why those independent returns are important. We’re using motorized valves on this installation (Fig. S) to isolate one boiler from the other. When either boiler needs water, the McDonnell & Miller pump controller on that boiler will drop to a point where it will close the higher of its two switches. That switch will power that boiler’s motorized valve, causing it to open. When it’s fully opened, the motorized valve will trip an end switch and start the boiler feed pump. Water will flow only to the boiler that needs it. The float in the pump controller will sense the rising water. When the water reaches the proper level, the pump controller will break the electrical connection to the motorized valve. The valve will begin to close, shutting off the boiler feed pump as it does.
As you can see, when we pipe multiple boilers this way it doesn’t matter how big or small each is. The boiler feed pump, although sized for the total needs of all the boilers, will satisfy the needs of each in turn, no matter what size.
Keeping the Water Flowing We’ve installed a make-up water feeder in the boiler feed pump’s receiver tank. It’s job is to maintain a minimum water line in the tank so the pump will always have a reservoir from which it can draw feed water. In this system, all the water will enter the boilers through the boiler feed pump. If, for any reason, the boiler feed pump can’t keep up with the boiler’s rate of evaporation, the water line in the boiler will drop. The lower switch in the McDonnell & Miller pump controller will stop the burner.

Basic System Operation

Pump Control and Low Water Cut-Off

Burner On

Motorized Valve
Steam Boiler No. 1

Feeder Cut-Off Pump Controller Combination

Pump Control and Low Water Cut-Off

Burner On

Motorized Valve
Steam Boiler No. 2

Multiple Boilers Boiler Feed Pump and Motorized Valves
fig. s

Pump Controller

Feeder Cut-Off Combination

City Water Supply Make-Up Water Feeder Boiler Feed Tank
Boiler Feed Pump
City Water Supply

Steam Boiler No.1

Motorized Valve

Steam Boiler No.2

Motorized Valve

Burner On

Burner On
Multiple Boilers Boiler Feed Pump, Motorized Valve & Water Feeders
fig. t

Make-Up Water Feeder
Boiler Feed Tank
Boiler Feeder Pump

Electric Proportioning
Regulator

Motor Operated Proportioning Valve

High Water Cut-Off and Alarm

Balancing Valve

Electric Proportioning
Regulator

Motor Operated Proportioning Valve

High Water Cut-Off and Alarm

Balancing Valve

Pump Return By-pass With Balancing Valve Orifice Or Relief Valve

City Water Supply

Steam Boiler No. 1

Steam Boiler No. 2

Boiler Feed Tank

Multiple Boilers

Boiler Feed Pump

Boiler Feed Pump, Electric Proportioning Regulators and Motorized Valves

Make-Up Water Feeder

fig. u 16

BBaassiicc SSyysstteemm OOppeerraattiioonn

Basic System Operation

If you find the pump suddenly can’t keep up with the boiler’s needs, check the temperature of the returning condensate. As thermostatic radiator steam traps and end of main F&T traps age and fail, they pass steam into the returns. That can make the condensate hot enough to “flash” when it hits the pump’s impeller. Boiler feed pumps can’t move water once it has flashed to steam. The pump will turn and cavitate, but it won’t satisfy the boiler.
Ideally, in a low pressure steam heating system, the condensate in the pump’s receiver shouldn’t be hotter than 180°F (82°C).
Multiple Boiler systems with a Boiler feed pump, Motorized Return valves and Boiler Water feeders (fig. t)
This is the same system we just looked at, except we’ve added a combination automatic water feeder and low water cut-off to a point just below the pump controller. The feeder/cut-off’s job will be to add water mechanically to the boiler should something happen to the boiler feed pump (for instance, if it’s cavitating because the return condensate is too hot).
Think of the feeder/cut-off as a back-up device to keep the boiler in operation should something go wrong elsewhere. The low water cut-off will back up the pump controller’s primary low water cut-off should something go wrong there, or if the feeder can’t keep up with the boiler’s rate of evaporation for some reason.

Multiple Boiler systems with a Boiler feed pump, Motorized Return valves and electric proportioning Regulator (fig. u)
Here we’re controlling the water lines with electric proportioning regulators. We’re matching the incoming feed water to the exact amount of water that’s leaving as steam. By doing this, we’re able to maintain a precise water line in both boilers and take advantage of each boiler’s full steaming space.
There are times when steaming loads will vary tremendously. This is especially true of steam heating systems in larger buildings. We often set up these buildings to operate on outdoor air temperature sensors and night set-back devices. When the system first starts in the morning the boilers will steam longer than they will during the day when the pipes and radiators are hot. This is also true of seasonal operation when you run the heating system less often.
This is when proportioning regulators can make a big difference. By closely monitoring the water line, regardless of varying system conditions, you improve the quality of steam leaving the boiler and allow the system to operate more efficiently.

Basic System Operation

Basic System Operation
Receiver tank control
If you size a boiler feed pump’s receiver properly it will be able to hold the right amount of water to keep the boiler operating during the start-up cycles. It will also be able to receive the returning condensate without overflowing.
Receiver sizing is more an art than a science. You have to look closely at the entire system to figure out how long it will take the condensate to return from the building. There are many variables to consider: The type and condition of steam traps, the pitch and cleanliness of steam mains and returns, the pipe insulation or lack of it, the shape of the building and how people use it.
There are also the times when you’ll have to deal with condensate transfer pumps, or maybe a vacuum/condensate pump. These pumps collect and relay return water back to the boiler feed pump. There are many things that can affect how quickly these secondary pumps move condensate back to the primary boiler feed pump. You have to consider them all when you’re sizing a feed pump receiver.
One thing will be a constant, however. There must always be enough water in the receiver for the boiler to draw from during the start-up cycle (the time between initial steaming and the return of condensate from the building). A McDonnell & Miller make-up feeder, set at the one-third full point on the receiver tank, will meet the boiler’s needs during this crucial start-up time. Let’s take a closer look at these.
Receiver tank Make-up Water feeders
Here, we’ve mounted a McDonnell & Miller make-up water feeder on a one-inch NPT equalizing line that extends from the top of the tank to the bottom. The level in the feeder’s chamber will be the same as the level in the tank. As the pump moves water out of the tank and into the boiler, the float inside the feeder’s chamber will open and constantly replenish the tank’s reservoir.
We’ve designed our feeders with the right amount of float and lever power to close tightly against city water pressure. This ensures that there will always be enough tank space to receive the returning condensate without having it overflow.
If the tank you’re using doesn’t have tappings for an equalizing line, you can use our internal feeder (Fig. V). As you can see, it mounts directly inside the tank and feeds water through its integral strainer. We make this unit with two flange sizes for both new and retrofit installations.
18

City Water Supply
Condensate Receiver Tank
Model 21 Make-Up Water
Feeder
Make-up Water feeder fig. v

Basic System Operation

A Make-up Water feeder used as a pilot valve
(fig. W)
When you have multiple boilers, the boiler feed pump has to be able to meet the needs of all the boilers should they need water simultaneously. During the start-up cycle, the draw from the feed pump’s receiver can be very heavy and the make-up feeder has to be able to match that flow.
When we run into this situation, we often use a make-up water feeder as a pilot valve to operate a high capacity diaphragm valve with “dead-end” service. When the feeder opens it signals the diaphragm valve to snap into action. The larger valve quickly maintains the receiver at the one-third full point. Once the feed pump shuts off the dead-end service valve closes tightly to prevent over filling. If returned condensate fills the receiver, the feed valve, of course, stays closed. This piping arrangement also gives you a lot of freedom because you can put the diaphragm valve in a remote location, if you’d like, for easier service.
A Make-up Water feeder with a Motorized valve
(fig. X)
Here’s another way you can quickly fill the receiver. Use a McDonnell & Miller controller to sense the tank’s water line. As the level rises and falls, the controller will electrically operate a high capacity motorized valve. This is another piping arrangement that gives you a lot of freedom. You can place that motorized valve anywhere you’d like.
low Water cut-offs for Receiver tanks
(fig. y)
There’s always the possibility for human error on any job. For instance, suppose someone decides to turn off the water supply to your receiver tank. The pump controller on the boiler will still start the pump, but once the receiver goes dry there won’t be any water to pump because of the closed valve. Or suppose the building loses water pressure and the feed pump suddenly finds itself moving more water than the water feeder can replace. If the pump runs dry, it will cavitate and its mechanical seal will quickly heat and break. That leaves you with a costly repair and system down time.
If you install a low water cut-off in an equalizing line around the tank, the cut-off will protect the pump no matter what happens.

Diaphragm Valve Check Valve

Needle Valve
City Water Supply Cond. Return

Large Condensate Receiver Tank

Model 25A Make-Up Water
Feeder

Make-up Water feeder Used as Pilot Valve
fig. W

City Water Supply

Motorized Valve

Large Condensate Receiver Tank
Model 93 Controller

Make-up Water feeder and Motorized Valve
fig. X

City Water Supply

Make-Up Water Feeder

Condensate Receiver Tank

Low Water Cut-Off

Boiler Feed Pump
low Water cut-off on Receiver Tank fig. y
19

Basic System Operation

hot Water Boilers
Low water protection isn’t just for steam boilers. Hot water boilers face the same perils of overheating damage if the water line drops too low. Many people don’t think of this as often as they should because hot water boilers serve “closed” systems. They have pressure reducing valves that are supposed to feed water automatically should a leak develop.
The truth, however, is that a pressure reducing valve is no substitute for a low water cut-off. Pressure reducing, or “feed” valves, often clog with sediment and wind up not feeding at all. A buried pipe can corrode and spring a leak that flows faster than a “feed” valve can satisfy. Relief valves can pop and, while dumping water at a great rate, actually prevent the feed valve from operating.
Let’s take a closer look at how we can protect these boilers.
hot Water systems (fig. Z)
As we said, the things that affect steam boilers also affect hot water boilers. If you run them with too much water the relief valve will open. If you run them with too little water they’ll overheat and suffer damage.
A low water cut-off is the only sure way of protecting a hot water boiler from sudden loss of water. The ASME boiler code recognizes this by requiring all hot water boilers of 400,000 BTU/HR or more input to have low water fuel cut- off devices.
ASME doesn’t call for low water cut-offs on smaller, residential boilers, but we think all hot water boilers, regardless of their size, must have protection. However, the International Mechanical Code requires low water cut- offs on All hot water and steam boilers. McDonnell & Miller make several devices, both float and probe type, that protect and meet the needs of any boiler whether it’s cast iron, steel, or copper construction (Fig. AA, BB, CC).
Hot water systems regularly lose water through faulty air vents, loose valve stem packing, cracked boiler sections, loose nipples, corroded pipes, broken or loose pump seals, leaking gaskets, dripping relief valves, to name just a few places. Most installers depend on their pressure reducing or feed valve, to replace the lost water automatically. But feed valves often clog with sediment, especially in hard water areas. And it’s very easy to close the supply valve to a feed valve and forget to open it again.

On systems with buried pipes (say, a radiant heating system) a feed valve will open if a pipe breaks. It will feed fresh water continuously until it either clogs (and stops feeding) or destroys the ferrous components of the system with oxygen corrosion. A simple feed valve can wind up costing a lot more than its purchase price. This is why major suppliers of feed valves, such as Bell & Gossett, recommend you close the feed valve once you’ve established your initial fill pressure.
This is also why we strongly recommend you use a low water cut-off on every hot water boiler. Feed valves are not a substitute for low water cut-offs. They can’t protect your boilers from a low water condition. Feed valves are fine for filling the system initially, and for helping you vent air from the radiators. But once the system is up and running, you shouldn’t look to them for protection.

Compression Tank

Cold Water Supply
Low Water Fuel Cut-Off
Series 63

Series RB or 750 Low Water Cut-Offs
Supply Main
ASME Relief Valve

Test-N-Check® Valves
Blow Down Valve

Hot Water Boiler

Burner On
hot Water Boiler fig. Z

Return Main

Basic System Operation

Basic System Operation
over firing
There are times when hot water boilers don’t lock-out on safety. Whether by control failure or human error, things go wrong. And when they go wrong in a hot water heating system, the water temperature can rise quickly to a point where the compression tank can’t take up the expansion of the water. This causes the relief valve to discharge.
When the relief valve opens, there’s a sudden drop in system pressure. The water, which at this point is probably much hotter than 212°F (100°C), will flash into steam. This is why ASME insists that relief valves for hot water boilers carry steam-discharge ratings.
If a feed valve doesn’t open to replace this rapidly exiting water, a low water condition will quickly result. The only thing that can protect the boiler at this point is a low water cut-off. The feed valve can’t protect the boiler because its typical setting is 12 psig (.83 bar). In other words, the system pressure must drop below 12 psig (.83 bar) before the feed valve will open.
The trouble is that while the relief valve is open and flashing steam to atmosphere, the internal system pressure never drops anywhere near 12 psig (.83 bar). A relief valve with a 30 psig (2.1 bar) setting, for instance, will open at 30 psig (2.1 bar), and close again when the pressure drops to about 26 psig (1.79 bar). The result is a loss of water with no make-up. Repeat this cycle enough times and the boiler will be in a dangerous, low water condition. Keep in mind, steam exerts pressure. It can easily fool a feed valve, and that’s why feed valves offer very little protection at all against low water.

series 67 float type low Water cut-off fig. AA
series 751p/752p probe type low Water cut-off fig. BB

series RB-24e probe type low Water cut-off fig. cc
21

Basic System Operation

feeder/cut-off combinations for cast iron and steel hot Water Boilers (fig. dd)
To protect a boiler from dry firing, the low water cut-off must located above the boiler’s crown. After the low water cut-off shuts off the burner, you should have a way to add water to the system to ensure the crown stays under water.
A combination water feeder and low water cut-off can do this for you. If you position the feeder above the boiler’s crown, it will mechanically feed water if the level should drop to that point. This is an important consideration because, even if the electricity is cut off, it’s possible for the firing cycle to continue if the fuel feed valve is mechanically locked open. The combination unit’s cut-off switch will act as a back-up to the primary low water cut-off, providing the boiler with additional protection.
protecting copper fin tube Boilers (fig. ee)
Copper fin tube boilers move heat from the flame to the water almost instantly. This type of boiler depends on the proper flow of water across its heat exchanger to move the heat quickly out of the boiler and into the system. Should flow stop while the burner is operating, heat will quickly build and cause the water in the heat exchanger to flash into steam. This condition is similar to a dry firing in a cast iron or steel boiler.
A McDonnell & Miller flow switch, installed on the copper fin tube boiler’s hot water outlet, protects it from this danger (Fig. FF). The burner cannot fire unless water is moving across the flow switch. When the flow stops, for whatever reason, the McDonnell & Miller flow switch immediately cuts electrical power to the burner and protects the boiler from overheating.

Compression Tank

City Water Supply
Feeder Cut-Off Combination
Model 247-2, 51-2, 51-S-2, 53-2
Water Level

Series RB or 750 Low Water Cut-Offs
Supply Main
ASME Relief Valve

Return
Burner On

Test-n-Check® Valves

Blow Down Valve

Return

hot Water Boiler fig. dd

Cold Water Supply

Compression Tank

Pressure Reducing Valve with Built-in Check Valve
Relief Valve Return from System

Circulating Pump

Flow Switch

Zone Control Valves

Flow

Flow Bypass Line
copper fin tube Boiler fig. ee

series fs4-3 flow switch (shown without paddle) fig. ff
22

Basic System Operation
pressure Relief valves
(Fig. GG, HH)
Good engineering practice calls for every hot water boiler to have a pressure relief valve. This spring-loaded valve must be able to release the boiler’s entire load at the boiler’s maximum operating pressure.
Here are some things that can cause a relief valve to open in a hot water heating system:
· The automatic feed valve fails, allowing higher than normal pressure to enter the system.
· Someone leaves a hand bypass line open after filling the system.
· Someone hydrostatically tests the system at a pressure greater than the relief valve’s setting.
· The air cushion in the diaphragm type compression tank doesn’t match the system’s static fill pressure. Keep in mind, most tanks come from the factory precharged at 12 psig (.83 bar). If the system needs more than 12 psig (.83 bar) pressure, you have to add more air to the tank, and you have to do this while you have the tank disconnected from the system.
· The compression tank may be too small for the system. · The boiler’s aquastat is in a well without heat
transfer grease. When this happens, the boiler’s temperature will quickly exceed the aquastat’s setting, causing rapid rise in system pressure. · The circulator may be on the return side of the system with the compression tank at its suction. If it is, the circulator’s head pressure will appear inside the boiler as a net increase. It may be enough to open the relief valve. · The burner limit may be jumped-out or stuck in a manual position.
The main thing to keep in mind when you’re troubleshooting this one is that relief valves pop when any of these three things happen:
· The compression tank loses it’s air cushion · The system takes on more water. · The system temperature increases.
Think methodically, and keep your eyes wide open!
We hope this Basic System Operation Guide has given you insight into the systems on which you’re now working or will face in the future. We welcome any questions or comments you may have about the Guide, or about our products.
Thanks for your support, and for your continuing business.

series 250 pressure Relief valve fig. GG
series 260 pressure Relief valve fig. hh
23

Basic System Operation

Boiler Controls

Boiler Controls
hot Water Boilers
McDonnell & Miller Low Water cut-offs are specially designed to protect hot water boilers from the hazards of a low water condition. In operation they will interrupt the electrical current to the firing device, if the water in the system drops below the boiler manufacturer’s minimum safe water level. Our low water cut-offs also provide an additional circuit for a low water alarm, should you desire to install one, for additional protection.
how to select low Water cut-offs for hot Water Boilers
Boiler pressure and the method of mounting are the primary factors to consider when selecting a low water cut-off.

Use the tapping designated by the boiler manufacturer for low water cut-off installation.
24

Boiler Controls

Steam Boilers

McDonnell & Miller Low Water Cut-offs are specially designed to protect steam boilers from the hazards of a low water condition. In operation they will interrupt the electrical current to the firing device, if the water in the system drops below the boiler manufacturers’ minimum safe water level.
Our low water cut-offs also provide an additional circuit for a water feeder or a low water alarm, should you desire to install one, for additional protection.

We recommend that secondary (redundant) Low Water Cut-Off controls be installed on all steam boilers with heat input greater than 400,000 BTU/hour or operating above 15 psi of steam pressure. At least two controls should be connected in series with the burner control circuit to provide safety redundancy protection should the boiler experience a low water condition. Moreover, at each annual outage, the low water cut-offs should be dismantled, inspected, cleaned, and checked for proper calibration and performance.

How to Select Low Water Cut-Offs for Steam Boilers
Boiler pressure and the method of installation are the primary factors to consider when selecting a low water cut-off.

Boiler Controls

Use the tapping designated by the boiler manufacturer for low water cut-off installation. 25

Boiler Controls

How to Select Controls
SteaM BOiLeRS
Steam Heating Boilers are classified as boilers in closed heating systems where all condensate is returned to the boiler. Best recommendation for all automatically fired boilers is a feeder cut-off combination. It adds water as needed to maintain a safe operating level, and stands by to interrupt circuit to burner if water level drops into emergency zone.
Steam Process Boilers are classified as boilers in systems where not all the condensate is returned, and some make-up water is needed. A separate feeder and separate cut-off are recommended, so operating levels can be set for the wider differential required in such service.
Selection of the correct feeder cut-off combination, or feeder depends upon:
1. Maximum boiler pressure.
2. Differential between water supply pressure and the pressure setting of the steam safety valve.
3. Boiler size
HOt WateR BOiLeRS
Best recommendation for all automatically fired boilers is a feeder cut-off combination. It adds water if needed to match the discharge capacity of the relief valve, and stands by to interrupt circuit to burner if water level drops into emergency zone.
Selection of the correct feeder cut-off combination, or feeder depends upon:
1. Maximum boiler pressure.
2. Differential between water supply pressure and the pressure setting of the safety relief valve.
3. Boiler size

BTU 33,475 66,950 167,375 251,063 334,750 418,438 502,125 585,813 669,500 836,875 1,004,250 1,171,625 1,339,000 1,506,375 1,673,750

Boiler Rating

EDR

140

280

700

7.5

1,050

1,400

12.5

1,750

2,100

17.5

2,450

2,800

3,500

4,200

4,900

5,600

6,300

7,000

Cond. Lb./Hr 34.5 69 173 259 345 431 518 604 690 863 1,035 1,208 1,380 1,553 1,725

Conversion Factors

Boiler Horsepower (BHP) =

EDR 139

Gallons of Water =

Lbs. of Water 8.33

BTUH = EDR x 240

EDR =

BTUH 240

BTUH = BHP x 33,479

Boiler Steaming Rate (Gallons Per Minute)

GPM =

EDR 2000

GPM = (BHP) x 0.069

GPM

BTU 480,000

GPM = EDR x 0.000496

Pounds of condensate per hour

EDR 4

Water Feeders and Combination Water Feeders/Low Water Cut-Offs
McDonnell & Miller Boiler Water Feeders and Feeder CutOff Combinations are used to provide automatic operation, and to safeguard steam and hot water boilers against the hazards of a low water condition.
A feeder cut-off combination mechanically adds water as needed to maintain the required minimum water level, and electrically stops the firing device in case of an emergency.

Boiler Controls

How to Select Water Feeders (continued)

Steam Boilers

Series Characteristics

Maximum Boiler
Pressure psi (kg/cm2)

10 (.7)

Boiler Size (Mfr. Gross Rating Sq. Ft. of EDR)
*Differential Pressure psi (kg/cm2)
20 (1.4) 30 (2.1) 40 (2.8) 50 (3.5) 60 (4.2)

Uni-Match® For Automatic Fired Heating Boilers

101A

For Automatic Fired Heating Boilers

For Heating or

Process Boilers

47-2 For Automatic Fired Heating Boilers

247 For Heating or Process Boilers

247-2 For Automatic Fired Heating Boilers

For Heating or

Process Boilers

51-2 For Automatic Fired Heating Boilers

51S For Heating or Process Boilers

51S-2 For Automatic Fired Heating Boilers

For Heating or

Process Boilers

53-2 For Automatic Fired Heating Boilers

15 (1.0) 25 (1.8) 25 (1.8) 25 (1.8) 30 (2.1) 30 (2.1) 35 (2.5) 35 (2.5) 35 (2.5) 35 (2.5) 75 (5.3) 75 (5.3)

8,600 8,600 10,500 10,500 8,600 8,600

12,000 12,000 17,500 17,500 11,600 11,600

All Boilers up to 5,000 sq. ft. All Boilers up to 5,000 sq. ft. All Boilers up to 5,000 sq. ft. All Boilers up to 5,000 sq. ft. All Boilers up to 5,000 sq. ft. All Boilers up to 5,000 sq. ft. 15,000 17,600 20,000 15,000 17,600 20,000 22,400 26,500 30,000 22,400 26,500 30,000 14,600 17,000 18,800 14,600 17,000 18,800

21,800 21,800 32,600 32,600 20,600 20,600

*Differential pressure should be based on water supply pressure at boiler, minus pressure setting of steam safety valve

70 (4.9)
23,400 23,400 35,000 35,000 22,100 22,100

Boiler Controls

Low Water Cut-Offs Electronic For Hot Water and Steam Boilers
Series 750

· For commercial or industrial applications · Primary or secondary control on hot water boilers · Secondary control (manual reset models only) on steam boilers · Manual reset models meet the requirements of ASME
Standard CSD-1. If the control is in a low water condition when there is an interruption of power, the control will remain in a low water condition when power is restored. The reset button will need to be pressed when the water level is restored to a level above the probe to allow the burner to fire. Standard Features · Green LED indicating power is on · Red LED indicating low water condition · Test button · No lock out with loss of power if probe is in water · 20,000 ohms sensitivity
Model 750-HW-MT-120

Series 750 Control Unit

A B

C D

Control Unit Temperature Ratings:
Temperature: Storage: -40°F to 120°F (-40°C to 49°C) Ambient: 32°F to 120°F (0°C to 49°C)
Humidity: 85% (non-condensing) Electrical Enclosure Rating: NEMA 1 General Purpose Hz: 50/60 Control Power Consumption: 3 VA (max.)

The 750-HW-MT-120 control provides continuous protection against a HIGHWATER condition in steam boilers and other water level applications. The manual reset function will require the unit be reset after water has risen above the level of the probe.

Electrical Ratings
Switch Rating (Amperes) Model Voltage Full Load Locked Rotor

24 VAC 24 VAC

—

120 VAC 120 VAC

7.5

43.2

Ordering Information

Model Number

Part Number Description

Weight lbs. (kg)

750-T-24 750-MT-24 750-T-120 750-MT-120 750-HW-MT-120

176294 176293 176206 176207 176236

LWCO – 24V Auto Reset LWCO – 24V Manual Reset LWCO – 120V Auto Reset LWCO – 120V Manual Reset HWCO – 120V Manual Reset

2 (.9) 2 (.9) 2 (.9) 2 (.9) 2 (.9)

(Remote sensor and probe rod must be ordered separately, see page 70-72)

Pilot Duty
50 VA at 24 VAC
125 VA at 120 VAC 50 or 60 Hz

Dimensions, in. (mm)

63/8 (162) 51/8 (130)

C 29/16 (65)

D 19/16 (40)

Boiler Controls

Low Water Cut-Offs Electronic For Hot Water and Steam Boilers

Series 751P/752P
· For commercial or industrial applications
· Primary or secondary control on hot water boilers
· Secondary control (manual reset models only) on steam boilers
· Manual reset models meet the requirements of ASME Standard CSD-1. If the control is in a low water condition when there is an interruption of power, the control will remain in a low water condition when power is restored. The reset button will need to be pressed when the water level is restored to a level above the probe to allow the burner to fire.
Standard Features
· Green LED indicating power is on
· Red LED indicating low water condition
· Test button
· Self cleaning probe
· No lock out with loss of power if probe is in water
· 20,000 ohms sensitivity

Electrical Ratings
Switch Rating (Amperes) Model Voltage Full Load Locked Rotor

24 VAC 24 VAC

—

120 VAC 120 VAC

7.5

43.2

Pilot Duty
50 VA at 24 VAC
125 VA at 120 VAC 50 or 60 Hz

A B
Series 751P/752P

CDE
F G

Probe Specifications
Maximum Steam Pressure: 15 psi (1.0 kg/cm2) Maximum Water Pressure: 160 psi (11.2 kg/cm2) Maximum Water Temperature: 250°F (121°C) Probe Sensitivity: 20,000 ohm
Control Unit Temperature Ratings:
Temperature: Storage: -40°F to 120°F (-40°C to 49°C) Ambient: 32°F to 120°F (0°C to 49°C)
Humidity: 85% (non-condensing) Electrical Enclosure Rating: NEMA 1 General Purpose Hz: 50/60 Control Power Consumption: 3 VA (max.)

Ordering Information
(Remote sensor must be ordered separately (see page 70-74)

Model Number

Part Number Description

752P-MT-24

176296

752P-MT-U-24 176298

752P-MT-SP-24 176297

751P-MT-120 176234

751P-MT-U-120 176214

751P-MT-SP-120 176295

LWCO – 24V w/standard probe LWCO – 24V w/ext. barrel probe (U’) LWCO – 24V w/short probe (SP’) LWCO – 120V w/standard probe LWCO – 120V w/ext. barrel probe (U’) LWCO – 120V w/short probe (SP’)

Weight lbs. (kg)
2.5 (1.1) 2.5 (1.1) 2.5 (1.1) 2.5 (1.1) 2.5 (1.1) 2.5 (1.1)

Dimensions, in. (mm)

Std.

NPT

65/8 (168) 55/16 (135) 23/4 (70) 19/16 (40) 31/16 (78) 19/16 (40) 21/8 (54) 15/16 (33) 19/16 (40)

3/4

G 7/8 (22)

Boiler Controls

Low Water Cut-Offs electronic For Steam Boilers

Series PSe-800
For commercial steam boiler applications

The Series PSE-800 probe type LWCO uses pantented technology to monitor changes in water conductivity. When defined parameters are exceeded the new PSE-800 makes a decision to shut the burner off based on the volatility/variability of the resistance settings. This new patented technology provides the best protection possible without turning off the boiler unless a low water condition exists. As an added measure of safety, the control will turn off the boiler if it recognizes an out-of-water condition when the sensivity threshold is exceeded.

Standard Features · Green LED indicating power is on · Red LED indicating low water condition · 30 second DOM · Test button · Self-Cleaning probe · No lock out with loss of power if probe is in water · Provisions to add water feeder of alarm
Models available with: · 120 VAC · 24 VAC (meets ANSIZ21. 13a specification) · U’ probe (extended barrel) ·RX2′ probe (remote)

Series PSe-800
Probe Specifications Maximum Steam Pressure: 15 psi (1.0 kg/cm2) Maximum Water Pressure: 160 psi (11.2 kg/cm2) Maximum Water temperature: 250°F (121°C) Probe Sensitivity: 7,000 ohm
Control Unit

electrical Ratings
Switch Rating (Amperes) Model Voltage Full Load Locked Rotor

24 VAC 24 VAC

—

Pilot Duty
50 VA at 24 VAC

temperature: Storage: -40°F to 120°F (-40°C to 49°C) Ambient: 32°F to 120°F (0°C to 49°C)
Humidity: 85% (non-condensing)

120 VAC 120 VAC

7.5

125 VA at

43.2

120 VAC

50 or 60 Hz

Ordering information

Model Number

Part Number

PSE-801-120 PSE-801-U-120 PSE-802-24 PSE-802-U-24 PSE-802-RX2-24

153827 153828 153927 153928 153929

Description
LWCO – 120V PSE-801-120 w/ext. barrel (U’ probe) LWCO – 24V PSE-802-24 w/ext barrel (U’ probe) PSE-802-24 w/remote sensor (`RX2′ probe)

Weight lbs. (kg)
2.7 (1.2) 2.7 (1.2) 2.7 (1.2) 2.7 (1.2) 2.7 (1.2)

Dimensions, in. (mm)

All

Std SP RX2 U

41/4 (108) 19/16 (40) 31/16 (78) 21/8 ( 54 ) 13/8 (35) 21/8 (54) 19/16 (40) 3/4 (20)

H All RX

/13 16 (21) / 51316 (148) 13/8 (35) 3/4 (20) 1/2 (25)

J 27/8 (73)

K 7/8 (22)

Boiler Controls

Low Water Cut-Offs electronic For Steam Boilers

PSe-800-M
Manual Reset LWCO

· Primary or Secondary control on hot water boilers · Secondary control on steam boilers · Manual reset models meet requirements of aSMe Standard
CSD-1. If the control is in a low water condition when there is an interruption of power, the control will remain in a low water condition when power is restored. The reset button will need to be pressed when the water level is restored to a level above the probe to allow the burner to fire.

Standard Features · Green LED indicating power is on · Red LED indicating low water condition · 60-second delay before lockout. · Test button · Self- Cleaning probe · No lock out with loss of power if probe is in water

Series PSe-800-M
Probe Specifications

electrical Ratings
Switch Rating (Amperes) Model Voltage Full Load Locked Rotor

24 VAC 24 VAC

—

120 VAC 120 VAC

7.5

43.2

Pilot Duty
50 VA at 24 VAC
125 VA at 120 VAC 50 or 60 Hz

Maximum Steam Pressure: 15 psi (1.0 kg/cm2) Maximum Water Pressure: 160 psi (11.2 kg/cm2) Maximum Water temperature: 250°F (121°C) Probe Sensitivity: 7,000 ohm
Control Unit
temperature: Storage: -40°F to 120°F (-40°C to 49°C) Ambient: 32°F to 120°F (0°C to 49°C)
Humidity: 85% (non-condensing)

· Probe Sensitivity: 7,000 ohms · Probe Consumption: 1.7 VA @ 24 VAC
3.6 VA @ 120 VAC · Enclosure Rating: NEMA 1 General Purpose

CaUtiON
Do not use “manual reset” models with electric automatic water feeders. Failure to follow this caution can cause flooding and property damage.

Ordering information

Model Number

Part Number Description

PSE-801-M-120 PSE-801-M-U-120 PSE-802-M-24 PSE-802-M-U-24

153601 153603 153602 153604

120V Manual Reset w/standard probe 120V Manual Reset w/ext. barrel probe (U’) 24V Manual Reset w/standard probe 24V Manual Reset w/ext. barrel probe (U’)

Weight lbs. (kg)
2.7 (1.2) 2.7 (1.2) 2.7 (1.2) 2.7 (1.2)

Dimensions, in. (mm)

A 41/4 (108)

All

U Std U

19/16 (40) 31/16 (78) 21/8 ( 54 ) 19/16 (40)

D 13/4 (20)

/13 15 (21) / 513 16 (148) 13/8 (35)

H 3/4 (20)

J 27/8 (73)

K 7/8 (22)

Boiler Controls

Low Water Cut-Offs electronic

RB-24e
Low Water Cut-Offs

· Brass threads enable a secure and trouble-free installation · Test button to confirm proper operation · Universal wiring harness fits 100% of today’s gas boilers · -S, -A, -B and -L models provide “plug & play” installation
with most residential boilers · Compact size · Easy to install and wire · Automatic reset feature resumes operations after a power
outage when water is on probe · Green LED indicating power is on · Red LED indicating low water condition · Solid state operation · 15,000 ohms probe sensitivity · Maximum ambient temperature 120°F (49°C) · Maximum water temperature 250°F (121°C) · Maximum water pressure of 160 psi (11.2 kg/cm2)

electrical Ratings

Voltage

Power Consumption

Load Switching

24 VAC

2.5 VA

2 A at 24 VAC

Note: A 15 mA minimum current draw is required.

Dimensions, in. (mm)

NPT

3/4

13/16 (30.2) 13/16 (30.2) 53/4 (180) 17/8 (47.6)

Ordering information

Model Number

Part Number

Description

RB-24E RB-24E-A RB-24E-B RB-24E-S RB-24E-L UWH-RB-24A UWH-RB-24B UWH-RB-24S UWH-RB-24L

144692 144694 144696 144693 144690 144681 144695 144682 144691

Residential LWCO Residential LWCO w/vent damper harness Residential LWCO w/burner control harness Residential LWCO w/control board harness Residential LWCO w/burner control harness Replacement cable for RB-24E-A Replacement cable for RB-24E-B Replacement cable for RB-24E-S Replacement cable for RB-24E-L

RB-24e
RB-24E-S
RB-24E-A
RB-24E-B RB-24E-L

D C B
E A
UWH-RB-24S
UWH-RB-24A
UWH-RB-24B UWH-RB-24L

Boiler Controls

Low Water Cut-Offs electronic For Hot Water Boilers

RB-122-e
Low Water Cut-Offs
· For residential and commercial applications · Electronic operation · Easy to install and wire · Red LED indicating low water condition · Green LED indicating power is on · Test button · Automatic reset · No blow down required · 20,000 ohms probe sensitivity · Maximum ambient temperature 120°F (49°C) · Maximum water temperature 250°F (121°C) · Maximum water pressure 160 psi (11.2 kg/cm2)

electrical Ratings

Voltage

Power Consumption

120 VAC

3.1 VA

Load Switching 5.8 A at 120 VAC

RB-122-e

H E

A D G

Dimensions, in. (mm)

23/4 (70)

15/8 (51)

C 13/8 (35)

Ordering information

Model

Part

Number Number Description

RB-122-E 144676 Low water cut-off

D 3/4 (20)

E 7/8 (22)

F 313/16 (99)

Weight lbs. (kg)
1.7 (.78)

NPT

3/4

33/16 (81)

Boiler Controls

Notes
Notes
34

Boiler Controls

Notes
Notes 35

Boiler Controls

Low Water Cut-Offs Mechanical For Steam Boilers
Series 61 ®
Low Water Cut-Offs

· For residential and commercial low pressure steam boiler applications
· For boilers of any steaming capacity
· Adjustable BX outlet for easy installation
· Dual precision switches for dependable operation of the low water cut-off and alarm or electric water feeder
· Packless bellows
· 1″ NPT equalizing pipes and blow down valve required
· Maximum steam pressure 20 psi (1.4 kg/cm2)

Series 61

E F

CUT-OFF LEVEL

electrical Ratings

Voltage 120 VAC 240 VAC

Motor Switch Rating (Amperes) Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty 125 VA at 120
or 240 VAC

Dimensions, in. (mm)

NPT

915/16 (252)

77/16 (189)

NPT

61/2 (165)

31/8 (79)

51/8 (130)

Ordering information

Model

Part

Number Number Description

140100 Low water cut-off

Weight lbs. (kg)
13.5 (6.1)

Boiler Controls

Boiler Controls
Low Water Cut-Offs Mechanical For Steam and Hot Water Boilers
Series 63
Low Water Cut-Offs
· For residential, commercial, and industrial applications · Heavy duty · Includes No. 2 switch · Optional manual reset available · Maximum boiler pressure 50 psi (3.5 kg/cm2) · Use with TC-4 on hot water systems

Series 63

CUT OFF LEVEL

J H
G D

electrical Ratings

Voltage 120 VAC 240 VAC

Motor Switch Rating (Amperes)

Full Load Locked Rotor

10.2

61.2

5.1

30.6

Pilot Duty 125 VA at 120 or 240 VAC
60 Hz

Dimensions, in. (mm)

NPT

61/2 (165)

29/16 (65)

NPT

55/32 (131)

93/8 (238)

31/8 (79)

101/2 (267)

51/8 (130)

Ordering information

Model Part Number Number Description

Weight lbs. (kg)

63 63-B 63-BM 63-M

142400 142700 143300 143100

Low water cut-off

13.5 (6.1)

63 w/ float block

15.0 (6.8)

63 w/float block & manual reset 15.0 (6.8)

63 w/manual reset

14.0 (6.4)

Boiler Controls

Low Water Cut-Offs Mechanical For Steam and Hot Water Boilers
Series 64
Low Water Cut-Offs

· For residential, commercial, and industrial boiler applications of any steaming capacity
· Heavy Duty · Adjustable BX outlet for easy installation · Dual precision switches for dependable operation of the
low water cut-off and alarm or electric water feeder · Packless bellows · Optional manual reset available · 1″ (25mm) NPT equalizing pipes required · Maximum boiler pressure 50 psi (3.5 kg/cm2) · Use with TC-4 on hot water systems

Dimensions, in. (mm)

NPT

915/16 (252) 77/16 (65)

61/2 (165) 31/8 (79)

®
SeRieS 64

A
B C

D E

CUT-OFF LEVEL

Model 64-a
Low Water Cut-Offs
· Quick hook-up fittings provided for installation directly into gauge glass tappings

Dimensions, in. (mm)

25/8 (66)

915/16 (252)

C 41/2 (113)

Model 64-a

min. 67/8 (172)

D max.
133/8 (339)

E 31/8 (79)

C G

D E

CUT-OFF LEVEL

NPT

Ordering information

Model

Part

Number Number Description

64 64-A 64-B 64-M

143600 143700 143800 144250

Low water cut-off 64 w/quick hook-up fittings 64 w/float block 64 w/manual reset

Weight lbs. (kg)
11.3 (5.1) 18.3 (8.3) 11.5 (5.2) 12.5 (5.7)

electrical Ratings

Voltage 120 VAC 240 VAC

Motor Switch Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
125 VA at 120 or 240 VAC

Boiler Controls

Low Water Cut-Offs Mechanical For Steam and Hot Water Boilers
Series 764
Low Water Cut-Offs
· For residential, commercial, and industrial boiler applications of any steaming capacity
· Heavy duty
· Adjustable BX outlet for easy installation
· Dual precision switches for dependable operation of the low water cut-off and alarm or electric water feeder
· Packless bellows
· 21/2″ NPT side tapping provided for installation with close nipple
· Maximum boiler pressure 50 psi (3.5 kg/cm2)

electrical Ratings

Voltage 120 VAC 240 VAC

Motor Switch Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
125 VA at 120 or 240 VAC

Series 764

B C

CUT OFF LEVEL

Dimensions, in. (mm)

NPT

67/8 (175)

61/2 (165)

31/8 (79)

21/2

Ordering information

Model

Part

Number Number

764

144500

Description Low water cut-off

Weight lbs. (kg)
12.5 (5.7)

Boiler Controls

Boiler Controls
Low Water Cut-Offs Mechanical For Steam Boilers
Series 67
Low Water Cut-Offs
· For residential and commercial applications · For boilers of any steaming capacity · Quick hook-up fittings provided · Lever-operated, full port ball valve for easy blow down · Adjustable BX outlet for easy installation · Dual precision switches for dependable operation of the
low water cut-off and alarm or electric water feeder · Optional features
Low voltage switches for self-generating millivolt circuits
Manual reset switch · Large float chamber · Maximum steam pressure 20 psi (1.4 kg/cm2)

electrical Ratings

Voltage 120 VAC 240 VAC

Motor Switch Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
125 VA at 120 or 240 VAC

Series 67

E C DF
G H
Max Swing

L
M N

K J

C EF

Model 67-LQHU (without quick hook-up fittings)

Max Swing

Dimensions, in. (mm)

min. max.

NPT

61/2 (165) 14 (356) 13/4 (45) 43/4 (121) 33/8 (86) 11/8 (29) 3/8

NPT

3/4 51/2 (140) 1/4 923/32 (247) 39/16 (90) 21/2 (64) 213/16 (71)

Ordering information

Model Part Number Number Description

Weight lbs. (kg)

149400

67-G 149600

67-LQHU 149500

67-M 149700

Low water cut-off 67 for millivolt service 67 without quick hook-up fittings 67 w/manual reset

10 (4.5) 10 (4.5) 8 (3.6) 10 (4.5)

Boiler Controls

Boiler Controls
Low Water Cut-Offs Mechanical For Steam Boilers
Series 767
Low Water Cut-Offs
· For residential and commercial low pressure boiler applications
· For boilers of any steaming capacity · 21/2″ NPT body tapping for side mounting on boilers · Lever-operated, full port ball valve for easy blow down · Adjustable BX outlet for easy installation · Dual precision switches for dependable operation of the
low water cut-off and alarm or electric water feeder · Large float chamber · Maximum steam pressure 20 psi (1.4 kg/cm2)

Series 767

E F G

K L M
P
(Max. Swing)

electrical Ratings

Voltage 120 VAC 240 VAC

Motor Switch Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
125 VA at 120 or 240 VAC

Dimensions, in. (mm)

NPT NPT

15/32 (29.3) 313/32 (186.5) 3/8

3/8

NPT

3/4 213/16 (71) 53/8 (137) 21/2

NPT

1/4 23/64 (51.9) 35/8 (92) 85/32 (207) 911/16 (246.6) 51/2 (140)

Ordering information

Model

Part

Number Number

Description

767

153700

Low water cut-off

Weight lbs. (kg)
8.5 (3.9)

Boiler Controls

Low Water Cut-Offs Mechanical For Steam Boilers
Series 69
Built-in Low Water Cut-Offs
· For residential and commercial low pressure steam boiler applications
· For boilers of any steaming capacity · For mounting in 21/2″ NPT boiler side tappings · Insertion lengths available in 13/16 – 41/8″ (30-105mm)
· Packless bellows
· Adjustable BX outlet for easy installation
· Dual precision switches for dependable operation of the low water cut-off and an alarm or electric water feeder
· Optional low voltage switches for self-generating millivolt circuits
· Maximum steam pressure 20 psi (1.4 kg/cm2)

electrical Ratings

Voltage 120 VAC 240 VAC

Motor Switch Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
125 VA at 120 or 240 VAC

Dimensions, in. (mm)

Insertion Model Length

69 41/8 (105) 169 31/8 (79) 269 21/4 (57) 369 13/4 (45) 469, 569 13/16 (30)

1 (25)

41/8 (105)

1/8 (3)

NPT

21/2 91/2 (241)

Ordering information

Model Part Number Number Description

153900

69-MV-P 155000 169 155100 269 155200 369 155300 369-MV 155400 469 155500 569 155700

Low water cut-off w/41/8″ (105mm)
insertion length
69 w/millivolt switch
69 w/31/8″ (79mm) insertion length 69 w/21/4″ (57mm) insertion length 69 w/13/4″ (45mm) insertion length
369 w/millivolt switch
69 w/13/16″ (30mm) insertion length 469 w/13/16″ (30mm) insertion length w/1/4″ NPT tapping

Weight lbs. (kg)
3.7 (1.7)
4.0 (1.8) 4.0 (1.8) 4.0 (1.8) 4.0 (1.8) 4.0 (1.8) 4.0 (1.8) 4.0 (1.8)

Series 69

F A

D
CUT-OFF LEVEL

Boiler Controls

Low Water Cut-Offs Combination Low Water Cut-Off/Pump Controllers for Steam Boilers

Series 42S

Low Water Cut-Off/Pump Controllers

· For residential, commercial, and industrial low and medium pressure steam boilers with a separate water column
· For boilers of any steaming capacity
· Monel bellows provides corrosion resistance
· Single pole, single throw snap action switches
· Enclosed junction box protects switches
· Optional features Quick hook-up fittings Gauge glass connector
· Maximum pressure 50 psi (3.5 kg/cm2)

SeRieS 42S

A B
C

E D
CUT-OFF LEVEL
F

electrical Ratings

Voltage 120 VAC 240 VAC

Pump Circuit Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
345 VA at 120 or 240 VAC

Alarm Circuit Rating (Amperes)

Voltage

Amps

120 VAC

240 VAC

1/2

MODeL 42S-a

Ordering information

Model Number 42S
42S-A 42S-N

Part Number 129302
129702 129802

Description

Weight lbs. (kg)

Combination low water cut-off/ 15.5 (7.0) pump controller

42S w/quick hook-up fittings 21.3 (9.7)

42S w/glass connector

21.3 (9.7)

MODeL 42S-N

Dimensions, in. (mm)

Model

42S 42S-A 42S-N

121/4 (311) 121/4 (311) 121/4 (311)

29/16 (65) 29/16 (65) 29/16 (65)

NPT

87/8 (225)

311/16 (94)

71/4-1611/16 (184-347) 23/4 (45)

87/8 (225)

311/16 (94)

DE F

C
CUT-OFF LEVEL
GC

BH Q

EL K
F

CUT-OFF LEVEL

D R

NPT

31/8 (79)

1/2

31/8 (79)

1/2

31/8 (79)

1/2

Model

NPT

42S-N 29/16 (65) 29/16 (65) 13/4 (45) 311/16 (94) 113/16 (46) 11/16 (27) 11/16 (27) 11/2 (38)

3/8

NPT

1/4

25/8 (67)

Boiler Controls
Low Water Cut-Offs Mechanical For Steam Boilers
Series 150S
Low Water Cut-Off/Pump Controllers
· For commercial and industrial low or high pressure boiler applications
· For boilers of any steaming capacity · Monel bellows provides corrosion resistance · Snap action switches for high temperature service
1 Single pole, single throw switch for pump control 1 Single pole, double throw switch for low water
cut-off and alarm actuation · Optional features
Manual reset 2 Single pole, single throw switches 2 Single pole, double throw switches Float block BSPT threads · Maximum pressure 150 psi (10.5 kg/cm2)
Model 150S-MD
Maximum differential operation Prevents nuisance burner shutdowns in low pressure applications operating less than 50 psi (3.5 kg/cm2)
· For additional information see page 46

®
Series 150S

Boiler Controls

electrical Ratings

Voltage 120 VAC 240 VAC

Pump Circuit Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
345 VA at 120 or 240 VAC

Ordering information

Model

Part

Number Number Description

150S

171702

150S-B

171903

150S-B-M 172803

150S-BMD 172002

150S-BM-MD 172805

150S-MD 171802

150S-M

172806

150S-M-MD 172807

158S

178402

158S-M

172819

159S

178802

Combination low water cut-off/ pump controller 150S w/float block 150S-B w/manual reset 150S w/float block and max. dif. 150S-BMD w/manual reset 150S w/maximum differential 150S w/manual reset 150S-M w/maximum differential 150S w/2 SPDT switches 158S w/manual reset 150S w/2 SPST switches

Weight lbs. (kg)
24.7 (11.2)
24.7 (11.2) 24.7 (11.2) 24.7 (11.2) 24.7 (11.2) 24.7 (11.2) 24.7 (11.2) 24.7 (11.2) 26.3 (11.9) 27.3 (12.4) 26.0 (11.8)

Alarm Circuit Rating (Amperes)

Voltage

Amps

120 VAC

240 VAC

1/2

Dimensions, in. (mm)

A 57/8 (149)

B 127/16 (316)

C 6 (152)

D 131/4 (337)

E 35/16 (84)

915/16 (252) 41/8 (105)

H 37/16 (87)

J 1 NPT

Boiler Controls

Low Water Cut-Offs Mechanical For Steam Boilers
Series 157S
Low Water Cut-Off/Pump Controllers
· For residential, commercial and industrial low or high pressure boiler applications
· For boilers of any steaming capacity · Monel bellows provides corrosion resistance · Float chamber with integral water column provided ·`Snap action for high temperature service
1 Single pole, single throw switch for pump control 1 Single pole, double throw switch for low water
cut-off and alarm actuation · Optional features
Manual reset Integral conductance probes for additional levels and
greater operating differential-Model 157S-RBP-MD 1″ or 11/4″ NPT equalizing tappings 1/2″ or 3/4″ NPT tappings for gauge glass/tri-cock
installations BSPTthreads · Maximum pressure 150 psi (10.5 kg/cm2)
Model 157S-MD
Maximum differential operation Prevents nuisance burner shutdowns in low pressure applications operating less than 50 psi (3.5 kg/cm2) For additional information see page 46

Series 157S

GJ H J

C K
D E
F

LA B
A

Model 157S-R

electrical Ratings

Ordering information

Voltage 120 VAC 240 VAC

Cut-off and Pump Circuits Rating (Amperes)

Full Load Locked Rotor

7.4

44.4

3.7

22.2

Pilot Duty
345 VA at 120 or 240 VAC

Alarm Circuit Rating (Amperes)

Voltage

Amps

120 VAC

240 VAC

1/2

Dimensions, in. (mm)

Model

Part

Number Number Description

Weight lbs. (kg)

157S

173502 150S low water cut-off w/water column 39.7 (18.0)

157S-MD 173603 157S w/maximum differential

39.7 (18.0)

157S-A

173702 157S w/alternate tappings

39.5 (17.9)

157S-A-M 172811 157S-A w/manual reset

39.5 (17.9)

157S-M

172812 157S w/manual reset

39.7 (18.0)

157S-M-MD 172813 157S-M w/maximum differential

39.7 (18.0)

157S-R

176220 157S w/alternate tappings

42.0 (19.0)

157S-R-M 172817 157S-R w/manual reset

42.0 (19.0)

157S-RBP-MD 176503 157S w/2 integral conductance probes 51.0 (23.1)

157S-RL

176902 157S w/alternate tappings

42.0 (19.0)

157S-RL-M 172815 157S-RL w/manual reset

42.0 (19.0)

Model

NPT

157S

157S-A

11/4

157S-R

157S-RL

11/4

NPT

1/2 133/8 (339) 25/16 (59) 415/16 (125) 113/4 (298) 16 (406) 111/2 (292) 31/2 (89) 3/4 57/8 (149) 3/4 133/8 (339) 25/16 (59) 415/16 (125) 113/4 (298) 16 (406) 111/2 (292) 31/2 (89) 3/4 57/8 (149) 1/2 133/8 (339) 21/4 (57) 57/8 (149) 113/4 (298) 17 (432) 111/2 (292) 31/2 (89) 3/4 61/4 (159) 1/2 139/16 (345) 31/2 (89) 57/8 (149) 113/4 (298) 17 (432) 123/4 (324) 31/2 (89) 3/4 61/4 (159)

Boiler Controls

MD Model Setpoints

The bellows on the 150 units are sensitive to pressure. At higher pressures the bellows is stiffer requiring more force to move it. At lower pressures the bellows is more pliable (less stiff) requiring less force to move it. Consequently, the on/off points tend to narrow at lower pressures. (Less distance between on and off).
Early versions of the 150 units with mercury bulb switches were able to be adjusted. These units had knurled adjustment screws that could be used to raise, lower or widen the setpoints. Although the available adjustment was small (usually 1/16″ to 1/8 ” total), it was enough to compensate in the field for lower pressure systems.

On MD’ models the distance between pump off and burner off is increased by approximately /7 16 “. Note that the pump on/off differential on both standard andMD’ models is set at 3/4″
This larger differential is accomplished by lowering the burner off setpoint 3/8 ” below the casting line on `MD’ models when setting the burner on/off points at 150 psi. This compensates for the narrowing of the setpoints at lower operating pressures because the burner off point will move upward (closer to the casting line) at lower pressures.

Later versions of the 150 with mercury bulb switches and all snap switch units are not adjustable in the field. The `MD’ models were created to provide a 150 control with factory settings to compensate for the narrowing of setpoints on new and existing installations.

Operating Levels Series 150/157 & Series 150S/157S

Standard Models

3/4″ Differential

“MD” Models

PUMP OFF PUMP ON

13/8″ Differential

Burner Off

Switch setpoints at 150psi

Burner 113/16″ Differential Off

Boiler Controls

Low Water Cut-Offs Mechanical For Steam Boilers
Series 1575
Low Water Cut-Off/Pump Controllers
· Primary low water fuel cut-off protection and pump control for commercial and industrial steam boilers
· Motorized valve controller, low water cut-off and alarm actuator for boilers, vessels and tanks
· Set points and differential remain constant throughout pressure range
· Diagnostic features incorporated in the control include: High ambient temperature protection Internal LEDs that indicate water position and condition External LEDs that indicate control activity
· Adjustable pump differentials by cutting probes to desired set points
· Control unit mounted remotely from probe chamber for maximum flexibility
· Adjustable 60-second burner-off time delay · 1 HP burner and pump relays · Solid state operation · Redundant low-water and pump-off circuitry · 60,000 ohms probe sensitivity · Test button to quickly confirm proper operation · Probe chamber with 3 probes and gauge glass tappings · 4th probe can be added for high water control · NEMA1 electrical control unit enclosure · NEMA4X probe chamber enclosure · Maximum ambient temperature 135ºF (57ºC) · Maximum water temperature 406ºF (208ºC) at probes · Maximum water pressure of 250 psi (17.6 kg/cm2)
Dimensions, in. (mm)
Probe Chamber

®
Probe Chamber (with 3 probes standard)
electrical Control Unit (for remote mounting)

NPT

185/8 (473) 111/2 (292) 31/8 (79) 21/2 (64) 31/4 (82) 43/8 (111) 43/16 (106)

electrical Control Unit

4 3/8″ (111)
4 3/16″ (106)

1/2 NPT
2 1/2″ (63)

1 NPT

3 5/16″ (159)

11 1/2″ (293)

18 5/8″ (473)

3 5/16″ (59)

1/2 NPT

3 1/8″ (79)

1 NPT

J NPT
1

61/2 (159) 53/16 (132) 23/4 (70) 3/4 (20)

electrical Rating and Switch Ratings

Supply Voltage

Probe Full load (Amps) Locked Rotor (Amps) Pilot Duty (VA) Voltage NO (NC), (VAC) NO (NC), (VAC) NO (NC), (VAC)

120 VAC 5 VAC

16 (5.8), 120

96 (34.8), 120

470 (290), 120

50/60Hz Maximum 8 (4.9), 240

48 (17.4), 240

470 (290), 240

Motor (HP) NO (NC), (VAC)
1 (1/4), 120 2 (1/2), 240

Ordering information

Model Number 1575

Part Number 171907

Description Combination LWCO/pump controller

Boiler Controls

Low Water Cut-Offs Mechanical Combination Low Water Cut-Off/Pump Controllers for Steam Boilers

Series 93

Low Water Cut-Off/Pump Controllers

· For commercial and industrial low or high pressure steam boilers
· Maintains consistent water level regardless of pressure · For boilers of any steaming capacity · No. 5 Switch included · Magnetic repulsion eliminates need for bellows · Optional features Manual reset · 7B switch (135ohm proportional control signal) to
maintain constant boiler water level · 1″ NPT connections · Maximum pressure 150 psi (10.5 kg/cm2)

SeRieS 93

B A E

CUT-OFF LEVEL 150
F

D C

electrical Ratings
345 VA at 120 or 240 VAC

Boiler Controls

Dimensions, in. (mm)

NPT

3/4

C 101/16 (256)

D 185/8 (473)

519/32 (142) 415/32 (113.5)

G 87/8 (225)

H 127/8 (327)

Ordering information

Model Part Number Number Description

93
93-M 93-7B 93-7B-M

162300
162500 163000 163100

Combination low water cut-off/ pump controller w/No. 5 switch
93 w/manual reset
93 w/No. 7B switch
93-7B W/manual reset

Weight lbs. (kg)
35.0 (15.9)
35.0 (15.9) 35.5 (16.0) 35.5 (16.0)

Boiler Controls

Low Water Cut-Offs Mechanical Combination Low Water Cut-Off/Pump Controllers for Steam Boilers

Series 193

Low Water Cut-Off/Pump Controllers

· For commercial and industrial low or high pressure steam boilers
· Maintains consistent water level regardless of pressure
· Water column with integral tappings for gauge glass and tri-cock installations
· For boilers of any steaming capacity · No. 5 Switch included · Magnetic repulsion eliminates need
for bellows · Optional features
Manual reset · 7B switch (135ohm proportional control
signal) to maintain constant boiler water level · 1″ NPT connections · Maximum pressure 150 psi (10.5 kg/cm2)
electrical Ratings
345 VA at 120 or 240 VAC
Dimensions, in. (mm)

M L
Q

CUT-OFF LEVEL 150

SeRieS 193

Ordering information

V U
T W
E G

B
CUT-OFF LEVEL
F
H

Model Number

Part Number Description

Weight lbs. (kg)

193
193-A 193-A-7B 193-A-7BM 193-A-M 193-B 193-B-M 193-B-7B 193-D 193-D-7B 193-M 193-7B 193-7BM 193-D-M 193-G

163400
163500 164500 164600 164200 163600 164300 164700 163900 163903 164100 164400 164525 163902 164760

Combination low water cut-off/ pump controller w/No. 5 switch 193 w/alternate tappings 193-A w/No. 7B switch 193-A-7B w/manual reset 193-A w/manual reset 193 w/alternate tappings 193-B w/manual reset 193-B w/No. 7B switch 193 w/alternate tappings 193-D w/No. 7B switch 193 w/manual reset 193 w/No. 7B switch 193-7B w/manual reset 193-D w/manual reset 193 w/alternate tappings

52.5 (23.8)
52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8) 52.5 (23.8)

Model
193 193-A 193-B 193-D 193-G

NPT

1/2

3/4

1/2

3/4

11/4

3/4

1/2

3/4

1/2

3/4

1/2

3/4

Model 193 193-A 193-B 193-D 193-G

L 123/4 (324)
123/4 (324)

M 111/2 (292)
111/2 (292) 111/2 (292)

N 1013/16 (274) 1013/16 (274) 1013/16 (274) 1013/16 (274) 1013/16 (274)

P 13 (330) 13 (330) 13 (330) 13 (330) 13 (330)

Q 21/4 (57)
21/4 (57) 21/4 (57)

R 27/8 (73)
27/8 (73)

Model 193 193-A 193-B 193-D 193-G

S 63/4 (171.4) 63/4 (171.4) 63/4 (171.4) 63/4 (171.4) 63/4 (171.4)

T 171/2 (445) 171/2 (445) 171/2 (445) 171/2 (445) 171/2 (445)

U 201/2 (521) 201/2 (521) 201/2 (521) 201/2 (521) 201/2 (521)

V 31/2 (89) 31/2 (89) 31/2 (89) 31/2 (89) 31/2 (89)

W 31/2 (89) 31/2 (89) 31/2 (89) 31/2 (89) 31/2 (89)

X 6 (152) 6 (152) 6 (152) 6 (152) 6 (152)

Boiler Controls

Low Water Cut-Offs Mechanical Combination Low Water Cut-Off/Pump Controllers for Steam Boilers

Series 94

Low Water Cut-Off/Pump Controllers

· For commercial and industrial low or high pressure steam boilers
· Maintains consistent water level regardless of pressure
· For boilers of any steaming capacity
· No. 5 Switch included
· Magnetic repulsion eliminates need for bellows
· Optional features Manual reset
· 7B switch (135ohm proportional control signal) to maintain constant boiler water level
BSPT threads · 11/4″ NPT connections
· Maximum pressure 250 psi (17.6 kg/cm2)
· Ten bolt flange

SeRieS 94

J KL

250 M

electrical Ratings
345 VA at 120 or 240 VAC

Ordering information

Model

Part

Number Number Description

94
94-A 94-AM 94-A-7B 94-M 94-7B

165200
165500 165800 165700 165900 166300

Combination low water cut-off/ pump controller w/No. 5 switch 94 w/alternate tappings 94-A w/manual reset 94-AM w/No. 7B switch 94 w/manual reset 94 w/No. 7B switch

Weight lbs. (kg)
52.5 (23.8)
50.3 (22.8) 50.3 (22.8) 52.5 (23.8) 52.5 (23.8) 52.0 (23.6)

E
MC FN

CUT-OFF LEVEL
N

Dimensions, in. (mm)

Model

6 (152) 7 (178)

94-A

6 (152) 7 (178)

109/16 (268) 1813/16 (478)

Model 94 94-A

E 57/8 (149) 57/8 (149)

F 411/16 (119) 411/16 (119)

G 83/4 (222) 83/4 (222)

H 1215/16 (328.6) 1215/16 (328.6)

Model

NPT

1/2 (15)

11/4

94-A

1/2 (15)

11/4

NPT

11/4

11/4 21/16 (52) 11/4 (32)

Boiler Controls

Low Water Cut-Offs Mechanical Combination Low Water Cut-Off/Pump Controllers for Steam Boilers

Series 194
Low Water Cut-Off/Pump Controllers
· For commercial, and industrial low or high pressure steam boilers
· Maintains consistent water level regardless of pressure
· For boilers of any steaming capacity
· Water column with integral tappings for gauge glass and tri-cock installations
· No. 5 Switch included
· Magnetic repulsion eliminates need for bellows
· Optional features Manual reset

SeRieS 194

K M

Q R
S

CUT-OFF LEVEL 250
N P

U V

LW T
E

B
CUT-OFF LEVEL
F

· 7B switch (135 ohm proportional signal) control to maintain constant boiler water level
· 11/4″ NPT connections · Maximum pressure 250 psi (17.6 kg/cm2) · Ten bolt flange
electrical Ratings
345 VA at 120 or 240 VAC

Ordering information

Model

Part

Number Number Description

Weight lbs. (kg)

194
194-A 194-A-7B 194-M 194-7B 194-7BM 194-B

166600
166700 167100 166900 167200 167300 166701

Combination low water cut-off/ 72.0 (32.7) pump controller w/Series 5 switch

194 w/alternate tappings

72.0 (32.7)

194-A w/Series 7B switch

72.0 (32.7)

194 w/manual reset

72.0 (32.7)

194 w/Series 7B switch

72.0 (32.7)

194-7B w/manual reset

72.0 (32.7)

194 w/alternate tappings

72.0 (32.7

Dimensions, in. (mm)

Model
194 194-A 194-B

NPT

11/4

1/2

11/4

1/2

11/4

3/4

NPT

1/2

3/4

1/2

3/4

1/2

3/4

Model 194 194-A 194-B

L 127/8 (327) 127/8 (327)

M 115/8 (295)

N 63/4 (171.4) 63/4 (171.4) 63/4 (171.4)

P 131/16 (332) 131/16 (332) 131/16 (332)

Q 213/16 (71) 213/16 (71) 213/16 (71)

R 11/4 (32) 11/4 (32) 11/4 (32)

S 23/8 (60) 23/8 (60) 23/8 (60)

Model 194 194-A 194-B

T 171/4 (438) 171/4 (438) 171/4 (438)

U 201/2 (521) 201/2 (521) 201/2 (521)

V 3 (76) 3 (76) 3 (76)

W 3 (76) 3 (76) 3 (76)

X 6 (152) 6 (152) 6 (152)

Y 1013/16 (274) 1013/16 (274) 1013/16 (274)
51

Boiler Controls
Water Feeders electronic
Series WFe Uni-Match®
· Field-adjustable dwell-feed cycles · Multi-Color LED status indicator · Manual feed button · Hard-stop limit to minimize chances of flooding the boiler · Compatible with all electronic & mechanical
Low Water Cut-Offs · Includes adapters for connection to 1/2″ copper tubing · Removable strainer (replace after cleaning) · Maximum water pressure 150 psi (10.5 kg/cm2) · Maximum boiler pressure 15 psi (1 kg/cm2) · Maximum water temperature 175°F (79.4°C) · Maximum ambient temperature 100°F (38°C) · Maximum power consumption (during water feed only)
15 VA at 24 VAC 20 VA at 120 VAC (50 or 60 Hz)

Series WFe

A D C
H B
EF G
K
J

Boiler Controls

Dimensions, in. (mm)

NPT

27/8 (73) 61/4 (159) 47/8 (124) 41/4 (108)

3/8

117/32 (39) 31/16 (78)

3/8

11/32 (26) 513/16 (148)

Ordering information

Model Number

Part Number Description

WFE-24 WFE-120

169550 169560

Electric Water Feeder, 24V Electric Water Feeder, 120V

Weight lbs. (kg)
2.8 (1.3) 2.8 (1.3)

Boiler Controls

Water Feeders electric
Series 101-a
electric Water Feeders
· For low pressure steam boilers with cold water feed · Eliminates necessity to manually add water to the boiler · Can be used with mechanical or electronic low water
cut-off controls · Quick-change replaceable cartridge valve and strainer · Manual feed button · Model 101-A features a 120 VAC solenoid · Model 101-A-24 features a 24 VAC solenoid and a
separate 50VA transformer · Maximum water supply pressure 150 psi (10.5 kg/cm2) · Maximum boiler pressure 25 psi (1.8 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum power consumption
40 VA at 24 VAC 40 VA at 120 VAC

Flow Data
Pressure Differential psi (kg/cm2)
5 (.4) 10 (.7) 20 (1.4) 40 (2.8) 60 (4.2) 80 (5.6)

Flow Rate gpm (lpm)
1.4 (5.3) 1.7 (6.4) 2.1 (7.9) 2.9 (11.0) 3.4 (12.9) 4.0 (15.1)

Dimensions, in. (mm)

41/16 (103)

67/8 (175)

C 51/8 (130)

D 79/16 (192)

Series 101-a

A G

C D
E

NPT

1/2

35/16

1/2

3 (76)

Ordering information

Model

Part

Number Number Description

101A

169400

101A-24V 169500

Electric water feeder, 120V Electric water feeder, 24V

Weight lbs. (kg)
2.8 (1.3) 2.8 (1.3)

Boiler Controls
Water Feeders Mechanical
®
Series 47/47-2
Mechanical Water Feeders/Low Water Cut-Offs
· For steam and hot water boilers with cold water feed · Continuous maintenance of minimum safe water level,
independent of electrical service · Proportional feed action · Quick hook-up fittings provided · Quick-change replaceable cartridge valve and strainer · Optional features
No. 2 switch Manual reset · Model 47 can be field upgraded with a No. 2 switch to add low water cut-off function · Maximum water supply pressure 150 psi (10.5 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum boiler pressure 25 psi (1.8 kg/cm2)

Series 47 Series 47-2

A B
D C

CLOSING LEVEL

E F

D C

CLOSING LEVEL

E F
G H

Boiler Controls

electrical Ratings

Motor Switch Rating (Amperes)

Voltage Full Load Locked Rotor

120 VAC

10.2

61.2

240 VAC

5.1

30.6

Pilot Duty
125 VA at 120 or 240 VAC
60 Hz

Dimensions, in. (mm)

117/8 (302)

51/4 (133)

H 75/16 (186) 54

J 45/8 (117)

C
73/8 (187) min. 14 (356) max.
K NPT 1/2

D 25/8 (67)
L 129/32 (58.4)

E NPT 3/4
M
113/32 (35.7)

N J

L M

B A

H TOP VIEW

51/8 (130)

105/8 (270)

N 3 (76)

P 55/16 (135)

Boiler Controls

Water Feeders Mechanical

Series 47 (continued)
Mechanical Water Feeders
Capacities

gpm (kg/hr.) lbs./hr. 8 (1814) 4,000

STEAM

BOILER

Sq. Ft.

Btu

(K-Calories/Hr.) (Kilowatts)

16,000

4,000,000 (15,900)

116 (1137)

6 (1361) 3,000 4 (907) 2,000 2 (454) 1,000

Maximum Capacity Capacity at Switch Cut-Off

12,000 8,000 4,000

3,000,000 (11,900)
2,000,000 (7,900)
1,000,000 (4,000)

87 (853)
58 (569)
29 (284)

(0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

Ordering information

Model

Part

Number Number Description

Weight lbs. (kg)

47 47-2 47-2-M 47-X 47-2X

132700 132800 132900 133400 176212

Mechanical water feeder

27.5 (12.5)

47 w/No. 2 switch

28.5 (13.0)

47-2 w/manual reset

28.5 (13.0)

47 w/o quick hook-up fittings 25.0 (11.4)

47-2 w/o quick hook-up fittings 26.0 (11.8)

Boiler Controls

Water Feeders Mechanical
Series 247/247-2
Mechanical Water Feeders/Low Water Cut-Offs
· For steam and hot water boilers with cold water feed · Continuous maintenance of minimum safe water level,
independent of electrical service · Proportional feed action · Quick-change replaceable cartridge valve and strainer · Quiet, durable operation · Isolated feed valve minimizes lime and scale build-up · Optional features
No. 2 switch Manual reset · Model 247 can be field upgraded with a No. 2 switch to add low water cut-off function · Maximum water supply pressure 150 psi (10.5 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum vessel pressure 30 psi (2.1 kg/cm2)

Series 247

B C

A F E

B C

A F E

Series 247-2

electrical Ratings

Motor Switch Rating (Amperes)

Voltage Full Load Locked Rotor

120 VAC

10.2

61.2

240 VAC

5.1

30.6

Pilot Duty
125 VA at 120 or 240 VAC
60 Hz

G
CLOSING LEVEL

K J

Dimensions, in. (mm)

NPT

61/2 (165)

91/8 (232) 51/8 (130) 45/8 (117) 25/8 (67) 75/16 (186)

1/2

113/32 (35.7) 129/32 (48.4)

Boiler Controls

Water Feeders Mechanical

Series 247 (continued)
Mechanical Water Feeders Capacities
gpm (kg/hr.) lbs./hr. 8 (1814) 4,000

STEAM

BOILER

Sq. Ft.

Btu

(K-Calories/Hr.) (Kilowatts)

16,000

4,000,000 (15,900)

116 (1137)

6 (1361) 3,000 4 (907) 2,000 2 (454) 1,000

Maximum Capacity Capacity at Switch Cut-Off

12,000 8,000 4,000

3,000,000 (11,900)
2,000,000 (7,900)
1,000,000 (4,000)

87 (853)
58 (569)
29 (284)

(0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

Ordering information

Model Number

Part Number Description

247 247-2 247-2-M

133700 133800 133900

Mechanical water feeder 247 w/No. 2 switch 247-2 w/manual reset

Weight lbs. (kg)
22.0 (10.0) 22.5 (10.2) 22.5 (10.2)

Boiler Controls

Water Feeders Mechanical

Series 51/51-2

Mechanical Water Feeders/Low Water Cut-Offs

· For low pressure steam and hot water boilers larger than 5,000 sq. ft. (465m2) capacity with cold water feed
· Quick-change replaceable cartridge valve and strainer
· Optional features No. 2 switch Manual reset Float block
· Proportional feed action
· Model 51 can be field upgraded with a No. 2 switch to add low water cut-off function
· Maximum water supply pressure 150 psi (10.5 kg/cm2)
· Maximum inlet water temperature 120°F (49°C)
· Maximum vessel pressure 35 psi (2.5 kg/cm2)

electrical Ratings

Motor Switch Rating (Amperes) Voltage Full Load Locked Rotor

120 VAC

10.2

61.2

240 VAC

5.1

30.6

Pilot Duty
125 VA at 120 or 240 VAC
60 Hz

Dimensions, in. (mm)

NPT

NPT NPT

8 (203) 103/8 (264) 53/4 (146) 1

3/4

Ordering information

Model

Part

Number Number Description

51 51-B 51-B-2 51-B-2-M 51-2 51-2-M

134700 134800 135400 135500 135000 135200

Mechanical water feeder 51 w/float block 51-B w/Series 2 switch 51-B-2 w/manual reset 51 w/Series 2 switch 51-2 w/manual reset

Weight lbs. (kg)
35.3 (16.0) 38.5 (17.5) 38.3 (17.4) 38.3 (17.4) 35.8 (16.2) 35.7 (16.2)

Series 51

CLOSING

LEVEL

D F
E

Series 51-2
Capacities

CLOSING

LEVEL

D F
E

FEEDER DISCHARGE gpm (kg/hr.) lbs./hr.

STEAM BOILER

Sq.Ft.

(Kilowatts)

20 (4536) 10,000 18 (4082) 9,000 16 (3629) 8,000

40,000 36,000 32,000

290 (2843)
261 (2559)
232 (2274)

14 (3175) 7,000 12 (2722) 6,000 10 (2268) 5,000
8 (1814) 4,000 6 (1361) 3,000 4 (907) 2,000 2 (454) 1,000

Maximum Capacity Capacity at Switch Cut-Off

28,000 24,000 20,000 16,000 12,000 8,000 4,000

203 (1990)
174 (1706)
145 (1421)
116 (1137)
87 (853)
58 (569)
29 (284)

0 (0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

Boiler Controls

Water Feeders Mechanical
Series 51-S/51-S-2
Mechanical Water Feeders/Low Water Cut-Offs
· For high capacity [up to 35,000 sq. ft. (3250m2)] low pressure steam and hot water boilers with cold water feed
· Optional features No. 2 switch Manual reset Float block
· Proportional feed action · Maximum water supply pressure 100 psi (7 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum vessel pressure 35 psi (2.5 kg/cm2)

Series 51-S

CLOSING

LEVEL

electrical Ratings

Motor Switch Rating (Amperes) Voltage Full Load Locked Rotor

120 VAC

10.2

61.2

240 VAC

5.1

30.6

Pilot Duty
125 VA at 120 or 240 VAC
60 Hz

CLOSING

LEVEL

Dimensions, in. (mm)

Series 51-S-2

NPT

81/8 (203) 103/8 (264) 53/4 (146)

3/4

Capacities

Ordering information

Model

Part

Number Number Description

51-S 51-S-2 51-S-2-M 51-SB 51-SB-2 51-SB-2-M

135600 135900 136000 135700 136300 136100

Mechanical water feeder 51-S w/No. 2 switch 51-S-2 w/manual reset 51-S w/float block 51-SB w/No. 2 switch 51-SB-2 w/manual reset

Weight lbs. (kg)
36.5 (16.6) 37.3 (16.9) 37.3 (16.9) 41.8 (19.0) 41.8 (19.0) 43.7 (19.8)

FEEDER DISCHARGE gpm (kg/hr.) lbs./hr.

STEAM BOILER

Sq.Ft.

(Kilowatts)

20 (4536) 10,000

40,000

18 (4082) 9,000 16 (3629) 8,000 14 (3175) 7,000 12 (2722) 6,000

Capacity mum

36,000 32,000 28,000 24,000

Maxi

10 (2268) 5,000

20,000

8 (1814) 4,000 6 (1361) 3,000 4 (907) 2,000

Capacity at Switch Cut-Off

16,000 12,000 8,000

2 (454) 1,000

4,000

(0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

290 (2843)
261 (2559)
232 (2274)
203 (1990)
174 (1706)
145 (1421)
116 (1137)
87 (853)
58 (569)
29 (284)
0

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

Boiler Controls

Water Feeders Mechanical
Series 53/53-2
Mechanical Water Feeders/Low Water Cut-Offs
· For low pressure steam and hot water boilers larger than 5,000 sq. ft. (465m2) with hot or cold water feed
· Optional features No. 2 switch Manual reset Float block
· Proportional feed action · Model 53 can be field upgraded with a No. 2 switch
to add low water cut-off function · Maximum water supply pressure 150 psi (10.5 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum vessel pressure 75 psi (5.3 kg/cm2)

Series 53

electrical Ratings

Motor Switch Rating (Amperes)

Voltage Full Load Locked Rotor

120 VAC

10.2

61.2

240 VAC

5.1

30.6

Pilot Duty
125 VA at 120 or 240 VAC
60 Hz

Dimensions, in. (mm)

NPT

NPT NPT

81/8 (206) 103/8 (264) 53/4 (146)

3/4

Series 53-2
Capacities

CLOSING

LEVEL

CLOSING

LEVEL

Ordering information

Model Part Number Number Description

53 53-B 53-B-2 53-B-2-M 53-2 53-2-M

136900 137400 137500 137600 137100 137200

Mechanical water feeder 53 w/float block 53-B w/No. 2 switch 53-B w/No. 2 switch & manual reset 53 w/No. 2 switch 53-2 w/manual reset

Weight lbs. (kg)
38.0 (17.2) 42.0 (19.0) 42.0 (19.0) 42.0 (19.0) 38.5 (17.5) 38.5 (17.5)

FEEDER DISCHARGE gpm (kg/hr.) lbs./hr.

STEAM BOILER

Sq.Ft.

(Kilowatts)

20 (4536) 10,000 18 (4082) 9,000 16 (3629) 8,000

40,000 36,000 32,000

290 (2843)
261 (2559)
232 (2274)

14 (3175) 7,000 12 (2722) 6,000 10 (2268) 5,000
8 (1814) 4,000 6 (1361) 3,000 4 (907) 2,000 2 (454) 1,000

Maximum Capacity Capacity at Switch Cut-Off

28,000 24,000 20,000 16,000 12,000 8,000 4,000

203 (1990)
174 (1706)
145 (1421)
116 (1137)
87 (853)
58 (569)
29 (284)

(0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

Boiler Controls

Make-Up Water Feeders

In boiler feed systems with higher pressures, a make-up feeder is usually provided on the condensate receiver. It adds water to the receiver when necessary so there is always an adequate supply for boiler demand.
McDonnell & Miller Make-up feeders provide large feeding capacity. Unless otherwise stated, valves and seats are of stainless steel and protected by a large integral strainer. Positive alignment of the valve is assured by cam & roller, straight thrust action. These feeders can be used for many other liquid control applications such as:
· Pharmaceutical
· Laboratory
· Industrial
· Distillation equipment
· Receiver tanks
· Evaporative coolers
· Humidifiers
· Aquariums
· Steam baths
· Wet and dry hygrometers

Water Feeding Capacity lbs./hr. (kg/hr.)

Model Number

10 (.7)

City Water Supply Pressure with 3/4″ NPT Pipe and No Tank Pressure, 0 psi (kg/cm2) 20 (1.4) 30 (2.1) 40 (2.8) 50 (3.5) 60 (4.1) 70 (4.8) 80 (5.5)

90 (6.2)

25-A 3100 (1406) 4500 (2041) 5600 (2540) 6550 (2971) 7400 (3357) 8150 (3697) 8800 (3992) 9400 (4264) 10200 (4627)

21 & 221 4100 (1860) 6000 (2722) 7500 (3402) 8600 (3901) 9600 (4355) 10500 (4763) 11300 (5126) 12000 (5443) 13200 (5988)

847

1000 (454) 1500 (680) 1800 (816) 2100 (953) 2400 (1089) 2600 (1179) 2800 (1270) 3000 (1361) 3300 (1497)

851

2000 (907) 3000 (1361) 3700 (1678) 4300 (1850) 4800 (2177)

—

851-S 3000 (1361) 4000 (1814) 5000 (2268) 6200 (2812)

—

551-S 2500 (1134) 3600 (1633) 4500 (2041) 5200 (2359) 5800 (2631) 6500 (2948) 7000 (3175) 7600 (3447) 8800 (3992)

Boiler Controls

Water Feeders Make-Up
Series 25-a
Make-Up Water Feeder
· For boiler receiver tanks · Float operated · Proportional feed action · Soft seat provides positive seal · Seal between float chamber and valve chamber is not
a positive seal · Maximum water supply pressure 100 psi (7 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum vessel pressure 35 psi (2.5 kg/cm2)

Series 25-a

J B H

Boiler Controls

Dimensions, in. (mm)

NPT

/13 16

(21)

3/4

121/4 (311) 81/8 (206)

Ordering information

Model

Part

Number Number Description

25-A 25-AB

126800 126900

Make-up water feeder 25-A w/float block

Weight lbs. (kg)
37.5 (17) 41.8 (19)

Capacities

FEEDER DISCHARGE (kg/hr.) lbs./hr. (4990) 11,000

BOILER

gpm

(lpm) (Kilowatts)

22 (83.27) 319 (3127)

(4536) 10,000

20 (75.70) 290 (2843)

(4082) 9,000 (3629) 8,000 (3175) 7,000 (2722) 6,000

Capacity Maximum

18 (68.13) 261 (2559) 16 (60.56) 232 (2274) 14 (52.99) 203 (1990) 12 (45.42) 174 (1706)

(2268) 5,000

10 (37.85) 145 (1421)

(1814) 4,000

8 (30.28) 116 (1137)

(1361) 3,000

6 (22.71) 87 (853)

(907) 2,000

4 (15.14) 58 (569)

(454) 1,000

2 (7.57) 29 (284)

(0)

0 (0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

WATER SUPPLY PRESSURE IN LBS. PER SQ. IN.

0 (0)

NPT

1/2 (12.7) 103/8 (264)

J NPT 3/4

Boiler Controls

Water Feeders Make-Up

Series 21
Make-Up Water Feeder
· For boiler receiver tanks

· Direct mounting eliminates need for equalizing connections

· Proportional feed action

· Mounting Flange six 7/16″ (11.1mm) bolt holes on a 53/4″ (146mm) bolt circle

· Soft seat provides positive seal

· Maximum water supply pressure 150 psi (10.5 kg/cm2)

· Maximum inlet water temperature 120°F (49°C)

· Maximum vessel pressure 35 psi (2.5 kg/cm2)

Dimensions, in. (mm)

81/2 (216)

35/16 (84)

55/8 (143)

813/16 (224)

Series 221
Make-Up Water Feeder

· For boiler receiver tanks · Direct mounting eliminates need for equalizing
connections · Proportional feed action · Mounting Flange six 17/32″ (13.5mm) bolt holes on a 81/2″
(216mm) bolt circle · Soft seat provides positive seal · Maximum water supply pressure 150 psi (10.5 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum vessel pressure 35 psi (2.5 kg/cm2)

Dimensions, in. (mm)

81/2 (216)

411/16 (84)

55/8 (143)

813/16 (224)

Capacities

(kg/hr.) lbs./hr.

CAPACITY CURVE

BOILER

gpm

(lpm) (Kilowatts)

(7258) 16,000

32 (121.12) 464 (4549)

(6804) 15,000

30 (113.55) 435 (4264)

(6350) 14,000

28 (105.98) 406 (3980)

(5897) 13,000

26 (98.41) 377 (3696)

(5443) 12,000

24 (90.84) 348 (3411)

(4990) 11,000

22 (83.27) 319 (3127)

(4536) 10,000

20 (75.70) 290 (2843)

(4082) 9,000

18 (68.13) 261 (2559)

(3629) 8,000

16 (60.56) 232 (2274)

(3175) 7,000

14 (52.99) 203 (1990)

(2722) 6,000

12 (45.42) 174 (1706)

(2268) 5,000

10 (37.85) 145 (1421)

(1814) 4,000

8 (30.28) 116 (1137)

(1361) 3,000

6 (22.71) 87 (853)

(907) 2,000

4 (15.14) 58 (569)

(454) 1,000

2 (7.57) 29 (284)

(0)

0 (0)

psi 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150

(kg/cm2) (0) (0.7)(1.4)(2.1)(2.8)(3.5)(4.2)(4.9)(5.6)(6.3)(7.0)(7.7)(8.4)(9.1)(9.8)(10.5)

WATER SUPPLY PRESSURE IN LBS. PER SQ. IN.

Series 21

E 43/4 (121)

F 61/4 (159)

NPT

3/4

73/8 (186)

Series 221

H B
E

E 43/4 (121)

F 61/4 (159)

G NPT 3/4 (20)

Ordering information

Model

Part

Number Number

Description

126400 Make-up water feeder

221

126600 Make-up water feeder

H
91/2 (241)
Weight lbs. (kg) 15.3 (6.9) 21.3 (9.7)

Boiler Controls

Water Feeders Make-Up
Series 847
Make-Up Water Feeder
· For receiver tanks in commercial or industrial applications · Mounts directly on the receiver, eliminating need for
equalizing connections · Quick-change replaceable cartridge valve and strainer · Proportional feed action · Mounting Flange six 7/16″ (11.1mm) bolt holes on a 53/4″
(146mm) bolt circle · Optional features
No. 2 switch Alternate valve orientation · Maximum supply pressure 150 psi (10.5 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum receiver pressure 25 psi (1.8 kg/cm2)

Series 847

WATER LINE

B
C E
D

Dimensions, in. (mm)

NPT

/5 16

(186)

415/16 (125)

45/8 (117)

39/16 (90)

1/2

37/16 (87)

Ordering information

Model

Part

Number Number Description

Weight lbs. (kg)

847 847-C 847-C-2

134300 134350 134400

Make-up water feeder

11 (5.0)

847 w/alternate valve orientation 12 (5.4)

847-C w/No. 2 switch

12 (5.4)

Capacities

gpm (kg/hr.) lbs./hr. 8 (1814) 4,000

STEAM

BOILER

Sq. Ft.

Btu/Hr.

(K-Calories/Hr.) (Kilowatts)

16,000

4,000,000 (15,800)

116 (1137)

6 (1361) 3,000 4 (907) 2,000 2 (454) 1,000

Maximum Capacity Capacity at Switch Cut-Off

12,000 8,000 4,000

3,000,000 (11,900)
2,000,000 (7,900)
1,000,000 (4,000)

87 (853)
58 (569)
29 (284)

(0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

Boiler Controls

Water Feeders Make-Up

Series 851
Make-Up Water Feeder

· For receiver tanks in commercial or industrial applications
· Mounts directly on the receiver, eliminating need for equalizing connections
· Quick-change replaceable cartridge valve and strainer · Proportional feed action · Mounting Flange six 7/16″ (11.1mm) bolt holes on a 53/4″
(146mm) bolt circle · Maximum water supply pressure 150 psi (10.5 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum receiver pressure 35 psi (2.5 kg/cm2)
Model 851-S
Make-Up Water Feeder
· Extended float and rod assembly · Wider operating range · Maximum water supply pressure 100 psi (7 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum receiver pressure 35 psi (2.5 kg/cm2)

Ordering information

Model Part Number Number Description

Weight lbs. (kg)

851 851-S

136700 Make-up water feeder

14 (6.4)

136800 851 w/extended float & rod assy. 16 (7.3)

Capacities Model 851

WATER LINE

E
Series 851
D

Dimensions, in. (mm)

NPT

113/4 (298) 415/16 (125) 45/8 (117) 39/16 (90) 3/4 37/16 (87)

Model 851-S

WATER LINE

B
C E
D

Dimensions, in. (mm)

NPT

123/4 (324) 415/16 (125) 33/16 (81) 39/16 (90) 3/4 37/16 (87)

Capacities Model 851-S

FEEDER DISCHARGE gpm (kg/hr.) lbs./hr.

STEAM BOILER

Sq.Ft.

(Kilowatts)

20 (4536) 10,000

40,000

18 (4082) 9,000

36,000

16 (3629) 8,000

32,000

14 (3175) 7,000

28,000

12 (2722) 6,000 10 (2268) 5,000
8 (1814) 4,000

Maximum Capacity

24,000 20,000 16,000

6 (1361) 3,000 4 (907) 2,000 2 (454) 1,000

Capacity at Switch Cut-Off

12,000 8,000 4,000

0 (0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

290 (2843)
261 (2559)
232 (2274)
203 (1990)
174 (1706)
145 (1421)
116 (1137)
87 (853)
58 (569)
29 (284)
0

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

FEEDER DISCHARGE gpm (kg/hr.) lbs./hr.

STEAM BOILER

Sq.Ft.

(Kilowatts)

20 (4536) 10,000 18 (4082) 9,000 16 (3629) 8,000 14 (3175) 7,000 12 (2722) 6,000 10 (2268) 5,000
8 (1814) 4,000 6 (1361) 3,000 4 (907) 2,000 2 (454) 1,000

Maxi

Capacity mum Capacity at Switch Cut-Off

40,000 36,000 32,000 28,000 24,000 20,000 16,000 12,000 8,000 4,000

290 (2843)
261 (2559)
232 (2274)
203 (1990)
174 (1706)
145 (1421)
116 (1137)
87 (853)
58 (569)
29 (284)

(0)

psi 0 10 20 30 40 50 60 70 80 90 100

(kg/cm2) (0) (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9) (5.6) (6.3) (7.0)

DIFFERENTIAL PRESSURE IN POUNDS PER SQ. IN. (Water pressure less boiler pressure)

Boiler Controls

Water Feeders Make-Up

Series 551-S
Make-Up Water Feeder
· For applications where water is added to steam separators, receivers, tanks, or other vessels
· Proportional feed action · Quick-change replaceable cartridge valve and strainer · Optional features
Float Block · Maximum water supply pressure 75 psi (5.3 kg/cm2) · Maximum inlet water temperature 120°F (49°C) · Maximum vessel pressure 25 psi (1.8 kg/cm2)

551-S

CLOSING LEVEL

Dimensions, in. (mm)

A 45/8 (117)

B 1/8 (3.2)

NPT

121/4 (311) 41/8 (105) 103/8 (264)

611/16 (170)

3/4

Ordering information

Model

Part

Number Number Description

551-S 551-SB

136400 136500

Make-up water feeder 551-S w/float block

Weight lbs. (kg)
35.8 (16.2) 35.8 (16.2)

Capacities

(kg/hr.) lbs./hr. (3175) 7,000

FEEDER DISCHARGE

BOILER

gpm

(lpm) (Kilowatts)

14 (52.99) 203 (1990)

(2722) 6,000 (2268) 5,000 (1814) 4,000 (1361) 3,000

Capacity Maximum

12 (45.42) 174 (1706) 10 (37.85) 145 (1421) 8 (30.28) 116 (1137) 6 (22.71) 87 (853)

(907) 2,000

4 (15.14) 58 (569)

(454) 1,000

2 (7.57) 29 (284)

(0)

psi 0

(kg/cm2) (0)

10 20 30 40 50 60 70 (.7) (1.4) (2.1) (2.8) (3.5) (4.2) (4.9)

WATER SUPPLY PRESSURE IN LBS. PER SQ. IN.

(Available city water supply pressure, or pump pressure, less internal pressure of unit on which control is installed)

0 (0)

Boiler Controls

Valves

Series 14-B Ball type
Blow Down Valve
· For McDonnell &Miller Series 47 and 67 boiler control blow down valve replacement
· Full-ported ball action valve · PTFE seats provide bind free, leak tight ball movement · Easy open handle keeps hands away from hot water
and steam · Gasket and mounting screws included · Maximum pressure 30 psi (1.8 kg/cm2) · See page 121 for blow-down information

Series 14-B

F E
B A
G
C 90¡
D

Dimensions, in. (mm)

NPT

63/4 (171.4) 4 (102) 21/4 (57) 3/4

21/2 (64) 21/2 (64) 53/4 (146)

Ordering information

Model

Part

Number Number

Description

14-B

310447

Blow down valve

Weight lbs. (kg)
1 (.5)

Boiler Controls

Series tC-4
test-N-Check® Valves

· For hot water boilers
· Simplifies ASME CSD-1 code mandated testing of low water cut-offs by eliminating the need to drain the system
· Includes one upper and one lower valve for mounting at crosses in equalizing lines
· Restricts water flow when the low water cut-off’s blow down valve is open
· Adjustable built-in vacuum breaker in upper valve provides rapid evacuation of water from the float chamber
· 1″ NPT
· Maximum temperature 250°F (121°C)
· Maximum pressure 160 psi (11 kg/cm2)

Dimensions, in. (mm)

NPT

11/2 (38)

5 (125)

NPT

Upper

Lower

51/4 (133)

31/16 (78)

Series tC-4 Upper Valve

Series tC-4 Lower Valve

Ordering information

Model

Part

Number Number Description

Weight lbs. (kg)

TC-4

195000 Test-N-Check Valves, set of 2 5.3 (.4)

Boiler Controls

Valves

OPEN POSITION

Series 250
Pressure Relief Valves

· For tanks and hydronic heating systems
· Protects against over-pressure
· Minimizes hammering with flash steam
· Low differential pressure 3 psi (.21 kg/cm2) between opening and closing
· Meets ASME Pressure Vessel and Boiler Code, Section IV
· Sizes and material 3/4″ – 1″ NPT bronze body and seat 2″ NPT cast iron body, brass seat
· EPDM rubber diaphragm and seat disc
· Maximum temperature 250°F (121°C)
· Maximum operating pressure range 30 – 125 psig (2.1 – 8.8 kg/cm2)

Series 250 3/4″ – 1″ (20-25mm) NPt

Dimensions, in. (mm)

Size

NPT

3/4

29/16 (65)

27/8 (73)

6 (152)

B
11/2 (38) 13/4 (45) 27/8 (73)

Series 250 2″ (50mm) NPt

3/4 (20) 7/8 (22) 31/4 (83)

49/16 (116) 415/16 (125) 11 (279)

DRAIN

C INLET

VACUUM BREAKER
NAME PLATE

DISCHARGE

C
BOILER
B A

11/32 (26) 11/32 (26)
—

23/32 (53.2) 21/4 (57)
—

Series 260
Pressure Relief Valves

· For water tanks and hydronic heating systems
· Protects against over-pressure
· Minimizes hammering with flash steam
· Low differential pressure 3 psi (.21 kg/cm2) between opening and closing
· Meets ASME Pressure Vessel and Boiler Code, Section IV
· Sealed spring chamber prevents scale or sediment build-up around seal
· 11/2″ NPT Inlet and 2″ NPT Discharge
· Cast iron body, brass seat
· Maximum temperature 250°F (121°C)
· Maximum operating pressure range 30 – 50 psig (2.1 – 3.5 kg/cm2)

DISCHARGE

Series 260

C
BOILER

Dimensions, in. (mm)

Size

NPT

Inlet Outlet

11/2

6 (152)

27/8 (73) 31/4 (83) 11 (279)

VACUUM BREAKER
NAME PLATE

Boiler Controls

BOiLeR CONtROLS
Boiler Controls Boiler Controls
Valves

Series 250
Pressure Relief Valves

Performance

Model Number

Opening Pressure psig (kg/cm2)

250-3/4IN-15 250-3/4IN-30 250-3/4IN-36 250-3/4IN-40 250-3/4IN-45 250-3/4IN-50 250-3/4IN-60 250-3/4IN-75 250-3/4IN-100 250-3/4IN-125
250-1IN-15 250-1IN-30 250-1IN-36 250-1IN-40 250-1IN-45 250-1IN-50 250-1IN-65 250-1IN-75 250-1IN-100 250-1IN-125
250-2IN-30 250-2IN-36 250-2IN-40 250-2IN-45 250-2IN-50

15 (1) 30 (2.1) 36 (2.5) 40 (2.8) 45 (3.2) 50 (3.5) 60 (4.2) 75 (5.3) 100 (7) 125 (8.8)
15 (1) 30 (2.1) 36 (2.5) 40 (2.8) 45 (3.2) 50 (3.5) 65 (4.6) 75 (5.3) 100 (7) 125 (8.8)
30 (2.1) 36 (2.5) 40 (2.8) 45 (3.2) 50 (3.5)

ASME Rating BTUH (K-Calories)

515,000 790,000 900,000 973,000 1,065,000 1,160,000 1,252,000 1,615,000 2,075,000 2,535,000
770,000 1,170,000 1,330,000 1,437,000 1,575,000 1,710, 000 2,110,000 2,385,000 3,060,000 3,735,000
4,100,000 4,600,000 5,000,000 5,500,000 5,900,000

(2,043) (3,134) (3,571) (3,861) (4,226) (4,603) (4,968) (6,409) (8,234) (11,059)
(3,056) (4,642) (5,278) (5,702) (6,250) (6,786) (8,373) (9,464) (12,142) (14,821)
(16,270) (18,254) (19,841) (21,825) (23,412)

Ordering information

Model

Part

Number Number Description

181220 181225 181325 181405 181425 181525 181905 181625 181725 181825
181920 181925 182025 182030 182125 182225 182235 182325 182425 182525
183025 183125 183175 183225 183325

Relief Valve 3/4 NPT, 15 psi (1 kg/cm2) Relief Valve 3/4 NPT, 30 psi (2.1 kg/cm2) Relief Valve 3/4 NPT, 36 psi (2.5 kg/cm2) Relief Valve 3/4 NPT, 40 psi (2.8 kg/cm2) Relief Valve 3/4 NPT, 45 psi (3.2 kg/cm2) Relief Valve 3/4 NPT, 50 psi (3.5 kg/cm2) Relief Valve 3/4 NPT, 60 psi (4.2 kg/cm2) Relief Valve 3/4 NPT, 75 psi (5.3 kg/cm2) Relief Valve 3/4 NPT, 100 psi (7 kg/cm2) Relief Valve 3/4 NPT, 125 psi (8.8 kg/cm2)
Relief Valve 1 NPT, 15 psi (1 kg/cm2) Relief Valve 1 NPT, 30 psi (2.1 kg/cm2) Relief Valve 1 NPT, 36 psi (2.5 kg/cm2) Relief Valve 1 NPT, 40 psi (2.8 kg/cm2) Relief Valve 1 NPT, 45 psi (3.2 kg/cm2) Relief Valve 1 NPT, 50 psi (3.5 kg/cm2) Relief Valve 1 NPT, 65 psi (4.6 kg/cm2) Relief Valve 1 NPT, 75 psi (5.3 kg/cm2) Relief Valve 1 NPT, 100 psi (7 kg/cm2) Relief Valve 1 NPT, 125 psi (8.8 kg/cm2)
Relief Valve 2 NPT, 30 psi (2.1 kg/cm2) Relief Valve 2 NPT, 36 psi (2.5 kg/cm2) Relief Valve 2 NPT, 40 psi (2.8 kg/cm2) Relief Valve 2 NPT, 45 psi (3.2 kg/cm2) Relief Valve 2 NPT, 50 psi (3.5 kg/cm2)

Weight lbs. (kg)
1.3 (.6) 1.3 (.6) 1.3 (.6) 1.3 (.6) 1.3 (.6) 1.3 (.6) 1.3 (.6) 1.3 (.6) 1.3 (.6) 1.3 (.6)
1.5 (.7) 1.5 (.7) 1.5 (.7) 1.5 (.7) 1.5 (.7) 1.5 (.7) 1.5 (.7) 1.5 (.7) 1.5 (.7) 1.5 (.7)
17.3 (7.8) 17.3 (7.8) 17.3 (7.8) 17.3 (7.8) 17.3 (7.8)

Series 260
Pressure Relief Valves

Performance

Model Number

Opening Pressure psig (kg/cm2)

260-1 1/2IN-30 260-1 1/2IN-36 260-1 1/2IN-40 260-1 1/2IN-45 260-1 1/2IN-50

30 (2.1) 36 (2.5) 40 (2.8) 45 (3.2) 50 (3.5)

ASME Rating BTUH (K-Calories)
3,300,000 (13,095) 3,800,000 (15,079) 4,100,000 (16,270) 4,500,000 (17,857) 4,900,000 (19,444)

Ordering information

Model

Part

Number Number Description

260-1 1/2IN-30 260-1 1/2IN-36 260-1 1/2IN-40 260-1 1/2IN-45 260-1 1/2IN-50

182625 182725 182730 182825 182925

Relief Valve 11/2 NPT, 30 psi (2.1 kg/cm2) Relief Valve 11/2 NPT, 36 psi (2.5 kg/cm2) Relief Valve 11/2 NPT, 40 psi (2.8 kg/cm2) Relief Valve 11/2 NPT, 45 psi (3.2 kg/cm2) Relief Valve 11/2 NPT, 50 psi (3.5 kg/cm2)

Weight lbs. (kg)
17.3 (7.8) 17.3 (7.8) 17.3 (7.8) 17.3 (7.8) 17.3 (7.8)

Liquid Level Controls

Remote Sensor Location
The location of the remote sensor is not limited to mounting on top of a tank. Depending on the application, it may be decided to mount the remote sensor in a stillwell or equalizing line. The following diagrams show typical locations for several applications.

Probe installation
All boiler manufacturers designate the preferred (and sometimes secondary) location for installation of the probe on their boiler. They have determined that this location is above the minimum safe water level and provides the 1/4″ clearance needed to ensure the probe is not grounded. Always install the probe in these locations, especially on a hot water boiler. If installed in other locations on a hot water boiler, this area could be prone to develop an air pocket.

Installation in piping external to the boiler on hot water systems has pitfalls. If the probe is too long and touches the wall of the pipe, the circuit is completed and the control “thinks” there is water in the system. If the water level drops below the level of the probe in this situation, the burner circuit will never be interrupted and a dry-fire could occur.

Open tanks or vessels will probably require mounting the remote sensor on a stillwell to dampen the liquids’ wave action. Use 3″ or 4″ perforated plastic drain pipe with a flange to thread connection at the top. The stillwell can rest on the bottom of the tank or be suspended and secured with brackets.

The most common problem with installation on hot water systems occurs when installing the probe in copper pipe. The sweat to thread adapters installed could result in the probe not being inserted in the pipe. An air pocket could develop or scale bridging could occur. While an air pocket causes nuisance shutdown of the boiler, scale bridging can result in a dry-fire if the water drops below the level of the probe. Always make sure at least 1/2 the length of the probe is in the run of the pipe to ensure proper operation.

Make sure tip of probe is in pipe with 1/4″ clearance from wall of pipe.

Liquid Level Controls

If probe is installed too close to boiler wall, an electrical short could occur.

Mounting the remote sensor in an equalizing pipe is an alternative to top mounting. The equalizing pipe should be at least a 2″ pipe and have a drain valve at the bottom for flushing.
70

If probe is installed with extensions, an air pocket could develop shutting down the boiler. Debris could develop which can cause an
electric short, rendering the low water cut-off ineffective.

Liquid Level Controls
Operation and Selection

A conductance-type control, Series 1575 will sense liquids up to 60,000 ohms resistivity. It can be used to activate a low level alarm, high level alarm, pumps to fill/drain a tank or any combination thereof. Typical applications include, but are not limited to, cooling towers, storage tanks, water fountains and condensate receivers.
The control utilizes the conductivity of a liquid to make or break circuits. Some liquids may be more resistive than the control can sense (above 60,000 ohms). The resistive and conductive properties of a liquid depend on several factors, including the amount of soluble material, temperature of the liquid, and placement of the probes. A TDS tester, which can be purchased from a supply house carrying boiler chemicals, is required to accurately measure a liquid’s resistivity.

Refer to the following charts to determine the resistivity of the liquid in an application. If it is above the 60,000 ohm rating, another type of control will be required.

Conductivity Values of Water

Liquid

Resistivity (Ohms/cm)

Water – Deionized

2,000,000

Water – Distilled

450,000

Water – Condensate

18,000

Water – Chlorinated

5,000

Water – Hard/Natural

5,000

Water – Sewage

5,000

Water – Salt

2,200

Conductivity (Micromhos/cm)
0.5 2 50 200 200 200 450

Control Unit
For many applications, water is the liquid being sensed. Raw or tap water usually has naturally occurring salts, chlorides and minerals that make it conductive enough to operate the control. Condensate receiver and cooling tower water are also very conductive due to evaporation. Ultrapure water (RO, deionized, demineralized, etc.) is highly resistive and is not able to conduct the current needed to operate the control.

Converting total Dissolved Solids to Resistivity and Conductivity

Total Dissolved Solids (ppm) 0.0277 0.0417 0.0833 0.500 1.25 10.0 100 1,000 10,000

Resistivity (Ohms/cm) 18,000,000 12,000,000 6,000,000 1,000,000
400,000 50,000 5,000
500 50

Conductivity (Micromhos/cm)
0.056 0.084 0.167 1.00 2.50 20.0 200 2,000 20,000

Liquid Level Controls

Series RS High Pressure Sensors & Probes For Conductance actuated Controls

Series RS S

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McDonnell And Miller MM-825J General Catalog

Product Information

Product Usage Instructions

FAQs

Basic System Operation

Boiler Controls

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